0000868857-25-000013 | 10-K | XBRL Viewer

Revenue Recognition (Tables)

12 Months Ended

Sep. 30, 2025

Revenue from Contract with Customer [Abstract]

Schedule of Revenues Disaggregated by Revenue Sources

The following tables present the Company’s revenues disaggregated by revenue sources:


	Fiscal Year Ended
	September 30, 2025		September 30, 2024		September 30, 2023

	(in millions)
Cost reimbursable	$	6,196.1	$	6,361.4	$	6,128.8
Guaranteed maximum price	5,960.7		6,030.0		4,887.7
Fixed price	3,982.8		3,714.1		3,362.0
Total revenue	$	16,139.6	$	16,105.5	$	14,378.5


	Fiscal Year Ended
	September 30, 2025		September 30, 2024		September 30, 2023

	(in millions)
Americas	$	12,526.4	$	12,487.0	$	10,976.4
Europe, Middle East, India, Africa	2,153.3		2,141.5		1,937.3
Asia-Australia-Pacific	1,459.9		1,477.0		1,464.8
Total revenue	$	16,139.6	$	16,105.5	$	14,378.5

Schedule of Net Accounts Receivable

Net accounts receivable consisted of the following:


	Fiscal Year Ended
	September 30, 2025		September 30, 2024

	(in millions)
Billed	$	1,934.3	$	2,184.9
Contract retentions	647.6		696.3
Total accounts receivable—gross	2,581.9		2,881.2
Allowance for doubtful accounts and credit losses	(84.8)		(87.9)
Total accounts receivable—net	$	2,497.1	$	2,793.3

Cover Page - USD ($) $ in Billions	12 Months Ended
Cover Page - USD ($) $ in Billions	Sep. 30, 2025	Nov. 14, 2025	Mar. 28, 2025
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Sep. 30, 2025
Current Fiscal Year End Date	--09-30
Document Transition Report	false
Entity File Number	000-52423
Entity Registrant Name	AECOM
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	61-1088522
Entity Address, Address Line One	13355 Noel Road
Entity Address, City or Town	Dallas
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	75240
City Area Code	972
Local Phone Number	788-1000
Title of 12(b) Security	Common Stock, $0.01 par value
Trading Symbol	ACM
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Document Financial Statement Error Correction [Flag]	false
Entity Shell Company	false
Entity Public Float			$ 12.2
Entity Common Stock, Shares Outstanding		131,833,332
Documents Incorporated by Reference	Part III incorporates information by reference from the registrant’s definitive proxy statement for the 2026 Annual Meeting of Stockholders, to be filed within 120 days of the registrant’s fiscal 2025 year-end.
Entity Central Index Key	0000868857
Document Fiscal Year Focus	2025
Document Fiscal Period Focus	FY
Amendment Flag	false

Leases - Schedule of Additional Balance Sheet Information Related to Leases (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Assets:
Operating lease assets	$ 463,479	$ 432,166
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Operating lease assets	Operating lease assets
Finance lease assets	$ 74,400	$ 62,100
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Property, Plant and Equipment, Net	Property, Plant and Equipment, Net
Total lease assets	$ 537,900	$ 494,300
Current:
Operating lease liabilities	$ 132,400	$ 135,100
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Accrued Liabilities, Current	Accrued Liabilities, Current
Finance lease liabilities	$ 31,900	$ 25,500
Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Long-Term Debt and Lease Obligation, Current	Long-Term Debt and Lease Obligation, Current
Total current lease liabilities	$ 164,300	$ 160,600
Non-current:
Operating lease liabilities	$ 515,998	$ 510,573
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Operating lease liabilities	Operating lease liabilities
Finance lease liabilities	$ 44,300	$ 35,700
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Long-term debt	Long-term debt
Total non-current lease liabilities	$ 560,300	$ 546,300
Weighted average remaining lease term (in years):
Operating leases (in years)	6 years 1 month 6 days	6 years 2 months 12 days	6 years 4 months 24 days
Finance leases (in years)	2 years 8 months 12 days	2 years 7 months 6 days	2 years 10 months 24 days
Weighted average discount rates:
Operating leases (as percent)	5.20%	5.10%	4.30%
Finance leases (as percent)	4.80%	4.40%	4.10%

Reportable Segments and Geographic Information (Tables)

12 Months Ended

Sep. 30, 2025

Segment Reporting [Abstract]

Schedule of Financial Information Concerning the Company's Reportable Segments

The following tables set forth summarized financial information concerning the Company’s reportable segments:


Reportable Segments:	Americas		International		AECOM Capital		Total
($ in millions)
Fiscal Year Ended September 30, 2025:
Revenue	$	12,525.9	$	3,613.2	$	0.5	$	16,139.6
Subcontractor and other direct costs	(7,973.7)		(593.1)		—		(8,566.8)
Employee compensation expense	(3,089.4)		(2,286.1)		—		(5,375.5)
Equity in earnings (losses) of joint ventures	15.8		11.8		(0.6)		27.0
Other segment items	(609.7)		(424.4)		(8.9)		(1,043.0)
Earnings before income taxes and amortization	$	868.9	$	321.4	$	(9.0)	$	1,181.3

Fiscal Year Ended September 30, 2024:
Revenue	$	12,485.7	$	3,618.4	$	1.4	$	16,105.5
Subcontractor and other direct costs	(8,281.1)		(659.4)		—		(8,940.5)
Employee compensation expense	(2,929.0)		(2,234.4)		(2.7)		(5,166.1)
Equity in earnings (losses) of joint ventures	15.5		13.5		(26.9)		2.1
Other segment items	(514.9)		(427.4)		(12.3)		(954.6)
Earnings before income taxes and amortization	$	776.2	$	310.7	$	(40.5)	$	1,046.4

Fiscal Year Ended September 30, 2023:
Revenue	$	10,975.7	$	3,402.1	$	0.7	$	14,378.5
Subcontractor and other direct costs	(7,056.7)		(619.0)		—		(7,675.7)
Employee compensation expense	(2,729.9)		(2,134.5)		(5.9)		(4,870.3)
Equity in earnings (losses) of joint ventures	14.8		9.7		(303.9)		(279.4)
Other segment items	(482.3)		(421.7)		(6.7)		(910.7)
Earnings before income taxes and amortization	$	721.6	$	236.6	$	(315.8)	$	642.4

Other segment items include rent expenses, depreciation, nonoperating income, and a deduction for earnings attributable to noncontrolling interests as well as other costs. The table below reconciles total segment attributable earnings before taxes and amortization to income from continuing operations before taxes:


	Fiscal Year Ended
	September 30, 2025		September 30, 2024		September 30, 2023
	(in millions)
Total segment attributable earnings before taxes and amortization	$	1,181.3	$	1,046.4	$	642.4
Corporate general and administrative expenses	(148.9)		(145.1)		(141.0)
Restructuring and acquisition costs	(59.4)		(98.9)		(188.4)
Other income	(2.5)		2.1		(5.3)
Interest income	62.9		58.6		40.3
Interest expense	(184.3)		(185.4)		(159.3)
Amortization expense	(2.2)		(18.8)		(18.6)
Income attributable to noncontrolling interests from continuing operations	68.7		59.3		43.3
Income from continuing operations before taxes	$	915.6	$	718.2	$	213.4


Reportable Segments:	Americas		International		AECOM Capital		Corporate and Assets Held for Sale		Total
	(in millions)
Fiscal Year Ended September 30, 2025:
Total assets	$	7,866.9	$	2,702.9	$	41.6	$	1,588.8	$	12,200.2
Investments in unconsolidated joint ventures	44.0		56.6		37.5		—		138.1

Depreciation and amortization	(94.3)		(70.8)		—		(10.8)		(175.9)

Fiscal Year Ended September 30, 2024:
Total assets	$	7,988.1	$	2,734.5	$	53.2	$	1,285.9	$	12,061.7
Investment in unconsolidated joint ventures	34.1		61.1		42.9		—		138.1

Depreciation and amortization	(101.6)		(67.2)		—		(10.0)		(178.8)

Fiscal Year Ended September 30, 2023:

Depreciation and amortization	(100.6)		(67.2)		—		(7.9)		(175.7)

Schedule of Geographic Information


	Fiscal Year Ended
Long-Lived Assets	September 30, 2025		September 30, 2024		September 30, 2023

	(in millions)
Americas	$	3,779.2	$	3,315.3	$	3,478.5
Europe, Middle East, India, Africa	1,025.5		872.9		803.5
Asia-Australia-Pacific	351.1		370.7		342.3
Total	$	5,155.8	$	4,558.9	$	4,624.3

Reportable Segments and Geographic Information

12 Months Ended

Sep. 30, 2025

Segment Reporting [Abstract]

Reportable Segments and Geographic Information

The Company manages its operations under three reportable segments according to their geographic regions and business activities. In identifying its reportable segments, the Company considered the financial information provided to its chief operating decision maker (CODM), who is the chief executive officer. The financial data is organized by geographic region and global business lines. The CODM uses this information to allocate resources and assess the performance of the segments primarily based on revenue less pass‑through revenue and attributable earnings before interest, tax, and amortization expense along with forecasts, market activity, and other non-financial information. Information provided to the CODM for purposes of making operating decisions and evaluating segment performance excludes asset-related information. After considering various factors, including the development and utilization of financial data to the CODM, the Company concluded that identifying its operating segments by geography was consistent with the objectives of ASC 280-10. Certain operating segments have been aggregated based on similar characteristics, including long-term financial performance, the nature of services provided, internal process for delivering those services, and types of customers, to arrive at the Company’s reportable segments. The Company’s Americas reportable segment provides planning, consulting, architectural and engineering design services, and construction management services to public and private clients in the United States, Canada, and Latin America and is comprised of the Design and Consulting Services Americas and Construction Management operating segments. The Company’s International reportable segment provides similar professional services to public and private clients in Europe and India, the Middle East and Africa, Asia, and Australia and New Zealand and is comprised of the operating segments in those geographic regions. The Company’s AECOM Capital (ACAP) operating segment is its own reportable segment and primarily invests in and develops real estate projects. Certain expenses that are determined to be related to the Company as a whole are not deemed to be part of an operating segment but are reported within Corporate.

The following tables set forth summarized financial information concerning the Company’s reportable segments:


Reportable Segments:	Americas		International		AECOM Capital		Total
($ in millions)
Fiscal Year Ended September 30, 2025:
Revenue	$	12,525.9	$	3,613.2	$	0.5	$	16,139.6
Subcontractor and other direct costs	(7,973.7)		(593.1)		—		(8,566.8)
Employee compensation expense	(3,089.4)		(2,286.1)		—		(5,375.5)
Equity in earnings (losses) of joint ventures	15.8		11.8		(0.6)		27.0
Other segment items	(609.7)		(424.4)		(8.9)		(1,043.0)
Earnings before income taxes and amortization	$	868.9	$	321.4	$	(9.0)	$	1,181.3

Fiscal Year Ended September 30, 2024:
Revenue	$	12,485.7	$	3,618.4	$	1.4	$	16,105.5
Subcontractor and other direct costs	(8,281.1)		(659.4)		—		(8,940.5)
Employee compensation expense	(2,929.0)		(2,234.4)		(2.7)		(5,166.1)
Equity in earnings (losses) of joint ventures	15.5		13.5		(26.9)		2.1
Other segment items	(514.9)		(427.4)		(12.3)		(954.6)
Earnings before income taxes and amortization	$	776.2	$	310.7	$	(40.5)	$	1,046.4

Fiscal Year Ended September 30, 2023:
Revenue	$	10,975.7	$	3,402.1	$	0.7	$	14,378.5
Subcontractor and other direct costs	(7,056.7)		(619.0)		—		(7,675.7)
Employee compensation expense	(2,729.9)		(2,134.5)		(5.9)		(4,870.3)
Equity in earnings (losses) of joint ventures	14.8		9.7		(303.9)		(279.4)
Other segment items	(482.3)		(421.7)		(6.7)		(910.7)
Earnings before income taxes and amortization	$	721.6	$	236.6	$	(315.8)	$	642.4


	Fiscal Year Ended
	September 30, 2025		September 30, 2024		September 30, 2023
	(in millions)
Total segment attributable earnings before taxes and amortization	$	1,181.3	$	1,046.4	$	642.4
Corporate general and administrative expenses	(148.9)		(145.1)		(141.0)
Restructuring and acquisition costs	(59.4)		(98.9)		(188.4)
Other income	(2.5)		2.1		(5.3)
Interest income	62.9		58.6		40.3
Interest expense	(184.3)		(185.4)		(159.3)
Amortization expense	(2.2)		(18.8)		(18.6)
Income attributable to noncontrolling interests from continuing operations	68.7		59.3		43.3
Income from continuing operations before taxes	$	915.6	$	718.2	$	213.4


Reportable Segments:	Americas		International		AECOM Capital		Corporate and Assets Held for Sale		Total
	(in millions)
Fiscal Year Ended September 30, 2025:
Total assets	$	7,866.9	$	2,702.9	$	41.6	$	1,588.8	$	12,200.2
Investments in unconsolidated joint ventures	44.0		56.6		37.5		—		138.1

Depreciation and amortization	(94.3)		(70.8)		—		(10.8)		(175.9)

Fiscal Year Ended September 30, 2024:
Total assets	$	7,988.1	$	2,734.5	$	53.2	$	1,285.9	$	12,061.7
Investment in unconsolidated joint ventures	34.1		61.1		42.9		—		138.1

Depreciation and amortization	(101.6)		(67.2)		—		(10.0)		(178.8)

Fiscal Year Ended September 30, 2023:

Depreciation and amortization	(100.6)		(67.2)		—		(7.9)		(175.7)

Geographic Information:


	Fiscal Year Ended
Long-Lived Assets	September 30, 2025		September 30, 2024		September 30, 2023

	(in millions)
Americas	$	3,779.2	$	3,315.3	$	3,478.5
Europe, Middle East, India, Africa	1,025.5		872.9		803.5
Asia-Australia-Pacific	351.1		370.7		342.3
Total	$	5,155.8	$	4,558.9	$	4,624.3

Long-lived assets consist of noncurrent assets excluding deferred tax assets.

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

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+ Details

Pension Benefit Obligations - Schedule of Reconciliations of Changes In the U.S. and International Plans' Benefit Obligations (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
U.S.
Change in benefit obligation:
Benefit obligation at beginning of year	$ 186.9	$ 181.2	$ 198.1
Service cost	0.0	0.0	0.0
Participant contributions	0.1	0.1	0.1
Interest cost	7.9	9.7	9.8
Benefits and expenses paid	(17.1)	(17.6)	(17.2)
Actuarial loss (gain)	(0.2)	13.5	(8.8)
Plan settlements	(0.7)	0.0	(1.5)
Transfers in	0.0	0.0	0.7
Foreign currency translation loss	0.0	0.0	0.0
Benefit obligation at end of year	176.9	186.9	181.2
Int’l
Change in benefit obligation:
Benefit obligation at beginning of year	860.4	756.2	791.2
Service cost	0.2	0.2	0.3
Participant contributions	0.2	0.3	0.2
Interest cost	40.1	43.7	47.7
Benefits and expenses paid	(46.2)	(47.7)	(42.2)
Actuarial loss (gain)	(69.8)	37.0	(112.5)
Plan settlements	0.0	(3.2)	(1.5)
Transfers in	0.0	0.0	0.0
Foreign currency translation loss	4.4	73.9	73.0
Benefit obligation at end of year	$ 789.3	$ 860.4	$ 756.2

Pension Benefit Obligations - Schedule of Reconciliation of Amounts In the Consolidated Statements of Stockholder's Equity (Details) - USD ($) $ in Millions	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
U.S.
Reconciliation of amounts in consolidated statements of stockholders’ equity:
Prior service cost	$ (0.1)	$ (0.1)	$ (0.1)
Net loss	(75.4)	(77.6)	(77.5)
Total recognized in accumulated other comprehensive loss	(75.5)	(77.7)	(77.6)
Int’l
Reconciliation of amounts in consolidated statements of stockholders’ equity:
Prior service cost	(1.2)	(1.3)	(1.2)
Net loss	(235.5)	(234.9)	(207.1)
Total recognized in accumulated other comprehensive loss	$ (236.7)	$ (236.2)	$ (208.3)

Revenue Recognition - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Passed through costs included in revenue and cost of sales	$ 8,600.0	$ 8,900.0	$ 7,700.0
Transaction price, allocated	19,700.0
Contract liabilities, revenue recognized	918.9	801.0
Significant claims recorded in contract assets and other non-current assets	400.0	180.0
Trade receivables sold with no financial and legal obligations	$ 268.2	$ 319.5
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation (as percent)	57.00%
Revenue, performance obligation expected timing of satisfaction period	12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2026-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, performance obligation expected timing of satisfaction period	2 years

Property and Equipment - Schedule of Property and Equipment, at Cost (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Sep. 30, 2024
Property and equipment
Total	$ 1,141,600	$ 1,061,200
Accumulated depreciation and amortization	(725,400)	(706,800)
Property and equipment, net	416,164	354,377
Building and land
Property and equipment
Total	$ 10,500	10,100
Building and land \| Minimum
Property and equipment
Useful Lives (years)	10 years
Building and land \| Maximum
Property and equipment
Useful Lives (years)	45 years
Leasehold improvements
Property and equipment
Total	$ 275,000	299,300
Leasehold improvements \| Minimum
Property and equipment
Useful Lives (years)	1 year
Leasehold improvements \| Maximum
Property and equipment
Useful Lives (years)	20 years
Computer systems and equipment
Property and equipment
Total	$ 770,400	659,600
Computer systems and equipment \| Minimum
Property and equipment
Useful Lives (years)	3 years
Computer systems and equipment \| Maximum
Property and equipment
Useful Lives (years)	12 years
Furniture and fixtures
Property and equipment
Total	$ 85,700	$ 92,200
Furniture and fixtures \| Minimum
Property and equipment
Useful Lives (years)	3 years
Furniture and fixtures \| Maximum
Property and equipment
Useful Lives (years)	10 years

Discontinued Operations, Goodwill and Intangible Assets (Tables)

12 Months Ended

Sep. 30, 2025

Discontinued Operations, Goodwill, and Intangible Assets [Abstract]

Schedule of Balance Sheet of Assets and Liabilities Held for Sale and Income Statement and Cash Flow Information of Discontinued Operations

The following table represents summarized balance sheet information of assets and liabilities held for sale (in millions):


	September 30, 2025		September 30, 2024
Cash and cash equivalents	$	—	$	4.0
Receivables and contract assets	—		73.2
Current assets held for sale	$	—	$	77.2

Investment in unconsolidated joint venture	$	18.9	$	—
Property and equipment, net	$	—	$	16.7
Other	0.1		1.2
Write-down of assets to fair value less cost to sell	—		(17.9)
Non-current assets held for sale	$	19.0	$	—

Accounts payable and accrued expenses	$	—	$	35.6
Current liabilities held for sale	$	—	$	35.6
Long-term liabilities held for sale	$	—	$	—

The following table represents summarized income statement information of discontinued operations (in millions):


	Fiscal Year Ended
	September 30, 2025		September 30, 2024		September 30, 2023
Revenue	$	97.6	$	178.2	$	212.8
Cost of revenue	101.4		181.1		223.2
Gross loss	(3.8)		(2.9)		(10.4)
Equity in losses of joint ventures	(10.1)		(3.4)		(2.9)
Loss on disposal activities	(83.8)		(97.1)		(50.6)
Transaction costs	—		(0.2)		(0.2)
Loss from operations	(97.7)		(103.6)		(64.1)
Other expense	(0.3)		(1.5)		(1.0)
Loss before taxes	(98.0)		(105.1)		(65.1)
Income tax benefit	(22.6)		(0.1)		(7.9)
Net loss from discontinued operations	$	(75.4)	$	(105.0)	$	(57.2)

The significant components included in the Consolidated Statement of Cash Flows for the discontinued operations are as follows (in millions):


	Fiscal Year Ended
	September 30, 2025		September 30, 2024		September 30, 2023
Payments for capital expenditures	$	—	$	(2.5)	$	(6.2)
Noncash increase in noncurrent assets held for sale due to deconsolidation of a joint venture	$	41.6	$	—	$	—
Noncash decrease in noncontrolling interest due to deconsolidation of a joint venture	$	(13.8)	$	—	$	—

Schedule of Changes in Carrying Value of Goodwill by Reportable Segment

The changes in the carrying value of goodwill by reportable segment for the year ended September 30, 2025 were as follows:


	September 30, 2024		Foreign Exchange Impact		Acquired		September 30, 2025

	(in millions)
Americas	$	2,625.7	$	(5.4)	$	150.1	$	2,770.4
International	854.5		0.4		75.3		930.2
Total	$	3,480.2	$	(5.0)	$	225.4	$	3,700.6

Schedule of Gross Amount and Accumulated Amortization of Acquired Identifiable Intangible Assets with Finite Useful Lives

The gross amounts and accumulated amortization of the Company’s acquired identifiable intangible assets with finite useful lives as of September 30, 2025 and 2024, included in intangible assets—net, in the accompanying consolidated balance sheets, were as follows:


	September 30, 2025						September 30, 2024
	Gross Amount		Accumulated Amortization		Intangible Assets, Net		Gross Amount		Accumulated Amortization		Intangible Assets, Net		Amortization Period

	(in millions)												(years)
Backlog and Customer relationships	$	7.4	$	(2.5)	$	4.9	$	671.7	$	(664.8)	$	6.9	1 - 11
Intellectual property	178.4		—		178.4		—		—		—		5
Total	$	185.8	$	(2.5)	$	183.3	$	671.7	$	(664.8)	$	6.9

Schedule of Estimated Amortization Expense of Intangible Assets

The following table presents estimated amortization expense of existing intangible assets for the succeeding years:


Fiscal Year	(in millions)
2026	$	37.2
2027	37.2
2028	37.2
2029	36.0
2030	35.7
Total	$	183.3

- Definition

Tabular disclosure of information related to a disposal group. Includes, but is not limited to, a discontinued operation, disposal classified as held-for-sale or disposed of by means other than sale or disposal of an individually significant component.

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+ Details

Debt (Tables)

12 Months Ended

Sep. 30, 2025

Debt Disclosure [Abstract]

Schedule of Debt

Debt consisted of the following:


	September 30, 2025		September 30, 2024

	(in millions)
Credit Agreement	$	1,439.9	$	1,446.6
2027 Senior Notes	—		997.3
2033 Senior Notes	1,200.0		—
Other debt	103.8		95.9
Total debt	2,743.7		2,539.8
Less: Current portion of debt and short-term borrowings	(66.3)		(66.9)
Less: Unamortized debt issuance costs	(30.2)		(22.6)
Long-term debt	$	2,647.2	$	2,450.3

Schedule of Maturities of Debt

The following table presents, in millions, scheduled maturities of the Company’s debt as of September 30, 2025:


Fiscal Year
2026	$	66.3
2027	31.2
2028	22.1
2029	761.3
2030	6.8
Thereafter	1,856.0
Total	$	2,743.7

Schedule of Debt Instrument Redemption

Furthermore, at any time on or after August 1, 2028, the Company may redeem on one or more occasions all or part of the 2033 Senior Notes at the redemption prices set forth below, plus accrued and unpaid interest thereon to, but excluding, the redemption date, if redeemed during the 12-month period beginning on August 1 of each of the years indicated below:


	Percentage
2028	103.000	%
2029	101.500	%
2030 and thereafter	100.000	%

Pension Benefit Obligations - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Defined Benefit Plan Disclosure [Line Items]
Aggregate contributions to multiemployer plans	$ 2.7	$ 2.5
U.S.
Defined Benefit Plan Disclosure [Line Items]
Expected employer contributions in next fiscal year	$ 10.8
Weighted-average long-term rate of return on assets assumption (as percent)	6.25%	6.90%	7.00%
Aggregate contributions to multiemployer plans	$ 10.6	$ 11.9	$ 8.2
Int’l
Defined Benefit Plan Disclosure [Line Items]
Expected employer contributions in next fiscal year	$ 25.0
Weighted-average long-term rate of return on assets assumption (as percent)	5.51%	5.74%	6.04%
Aggregate contributions to multiemployer plans	$ 23.7	$ 25.1	$ 24.8
Pension Plan, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Applicable deferred income taxes, included in OCI arising from net prior service cost and net gain/loss	$ 1.1	$ 2.1	$ 3.1

- Definition

Amount of contribution received by defined benefit plan from employer which increases plan assets.

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-Subparagraph (c)(iv)(02)
-Publisher FASB
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
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Reference 14: http://www.xbrl.org/2003/role/disclosureRef
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Reference 19: http://www.xbrl.org/2003/role/disclosureRef
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Reference 20: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Major Clients (Details) - Revenue - Customer Concentration Risk	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Percentage of total revenue
Period for which criteria of threshold percentage for disclosure not met in past	5 years
Agencies of U.S. Federal Government
Percentage of total revenue
Concentration risk (as percent)	7.00%	7.00%	5.00%

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 275
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (a)
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 275
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-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478785/954-310-50-2

+ Details

- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References + Details

Other Financial Information

12 Months Ended

Sep. 30, 2025

Other Financial Information [Abstract]

Other Financial Information

Accrued expenses and other current liabilities consist of the following:


	Fiscal Year Ended
	September 30, 2025		September 30, 2024

	(in millions)
Accrued salaries and benefits	$	727.0	$	620.4
Accrued contract costs	1,419.0		1,354.7
Other accrued expenses	344.5		410.6
	$	2,490.5	$	2,385.7

Accrued contract costs above include balances related to professional liability accruals of $893.7 million and $831.8 million as of September 30, 2025 and 2024, respectively. The remaining accrued contract costs primarily relate to costs for services provided by subcontractors and other non-employees. Liabilities recorded related to accrued contract losses were not material as of September 30, 2025 and 2024. The Company did not have material revisions to estimates for contracts where revenue is recognized using the input method during the twelve months ended September 30, 2025 and 2024. For the year ended September 30, 2025, the Company incurred restructuring and acquisition expenses of $59.4 million, which included labor-related costs of $32.0 million and non-labor costs of $27.3 million, of which $15.0 million was accrued and unpaid at September 30, 2025. For the year ended September 30, 2024, the Company incurred restructuring expenses of $98.9 million, which included labor-related costs of $18.7 million and non-labor costs of $80.2 million, of which $11.9 million was accrued and unpaid at September 30, 2024.

On September 10, 2025, the Company’s Board of Directors declared a quarterly cash dividend of $0.26 per share, which was paid on October 17, 2025 to stockholders of record as of the close of business on October 1, 2025. As of September 30, 2025, accrued and unpaid dividends totaled $37.6 million and were classified within other accrued expenses on the consolidated balance sheet. On November 18, 2025, the Company's Board of Directors declared a quarterly cash dividend of $0.31 per share. The dividend is payable on January 23, 2026 to stockholders of record as of the close of business on January 7, 2026.

Concentration of Credit Risk	12 Months Ended
Concentration of Credit Risk	Sep. 30, 2025
Risks and Uncertainties [Abstract]
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments which potentially subject the Company to concentrations of credit risk consist principally of cash investments and trade receivables. The Company’s cash balances and short-term investments are maintained in accounts held by major banks and financial institutions located primarily in the U.S., Canada, Europe, Australia, Middle East and Hong Kong. If the Company extends significant credit to clients in a specific geographic area or industry, the Company may experience disproportionately high levels of default if those clients are adversely affected by factors particular to their geographic area or industry. Concentrations of credit risk with respect to trade receivables are limited due to the large number of customers comprising the Company’s customer base, including, in large part, governments, government agencies and quasi-government organizations, and their dispersion across many different industries and geographies. See Note 4 regarding the Company’s foreign revenues. In order to mitigate credit risk, the Company continually reviews the credit worthiness of its major private clients. Major Clients No single client accounted for 10% or more of the Company’s revenue in any of the past five fiscal years. Approximately 7%, 7%, and 5% of the Company’s revenue was derived through direct contracts with agencies of the U.S. federal government in the years ended September 30, 2025, 2024 and 2023, respectively.

- Definition

The entire disclosure for any concentrations existing at the date of the financial statements that make an entity vulnerable to a reasonably possible, near-term, severe impact. This disclosure informs financial statement users about the general nature of the risk associated with the concentration, and may indicate the percentage of concentration risk as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Subparagraph (d)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-21

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
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-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Subparagraph (d)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-21

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
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-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Subparagraph (c)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-21

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Subparagraph (c)(2)
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
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-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-21

Reference 6: http://www.xbrl.org/2003/role/exampleRef
-Topic 275
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-Name Accounting Standards Codification
-Section 55
-Paragraph 3A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482836/275-10-55-3A

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 275
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-Name Accounting Standards Codification
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 275
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-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-1

Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 275
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org/275/tableOfContent

+ Details

Other Financial Information (Tables)

12 Months Ended

Sep. 30, 2025

Other Financial Information [Abstract]

Schedule of Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consist of the following:


	Fiscal Year Ended
	September 30, 2025		September 30, 2024

	(in millions)
Accrued salaries and benefits	$	727.0	$	620.4
Accrued contract costs	1,419.0		1,354.7
Other accrued expenses	344.5		410.6
	$	2,490.5	$	2,385.7

Reclassifications out of Accumulated Other Comprehensive Loss

12 Months Ended

Sep. 30, 2025

Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]

Reclassifications out of Accumulated Other Comprehensive Loss

The accumulated balances and reporting period activities for the years ended September 30, 2025, 2024 and 2023 related to reclassifications out of accumulated other comprehensive loss are summarized as follows (in millions):


	Pension Related Adjustments		Foreign Currency Translation Adjustments		Loss on Derivative Instruments		Accumulated Other Comprehensive Loss
Balances at September 30, 2022	$	(217.3)	$	(799.3)	$	36.9	$	(979.7)
Other comprehensive income (loss) before reclassification	(10.9)		59.6		10.7		59.4
Amounts reclassified from accumulated other comprehensive loss	2.2		—		(8.5)		(6.3)
Balances at September 30, 2023	$	(226.0)	$	(739.7)	$	39.1	$	(926.6)


	Pension Related Adjustments		Foreign Currency Translation Adjustments		Loss on Derivative Instruments		Accumulated Other Comprehensive Loss
Balances at September 30, 2023	$	(226.0)	$	(739.7)	$	39.1	$	(926.6)
Other comprehensive (loss) income before reclassification	(26.6)		93.2		(10.6)		56.0
Amounts reclassified from accumulated other comprehensive loss	0.6		—		(12.7)		(12.1)
Balances at September 30, 2024	$	(252.0)	$	(646.5)	$	15.8	$	(882.7)


	Pension Related Adjustments		Foreign Currency Translation Adjustments		Loss on Derivative Instruments		Accumulated Other Comprehensive Loss
Balances at September 30, 2024	$	(252.0)	$	(646.5)	$	15.8	$	(882.7)
Other comprehensive (loss) income before reclassification	(1.3)		(5.9)		4.8		(2.4)
Amounts reclassified from accumulated other comprehensive loss	1.9		—		(9.8)		(7.9)
Balances at September 30, 2025	$	(251.4)	$	(652.4)	$	10.8	$	(893.0)

Joint Ventures and Variable Interest Entities - Schedule of Financial Information of Unconsolidated Joint Ventures Derived from Unaudited Financial Statements (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Joint Ventures and Variable Interest Entities [Line Items]
Current assets	$ 6,730,227	$ 7,055,759
TOTAL ASSETS	12,200,249	12,061,669
Current liabilities	5,928,816	6,374,081
TOTAL LIABILITIES	9,504,065	9,691,259
Joint ventures’ equity	2,696,184	2,370,410	$ 2,383,711	$ 2,605,379
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	12,200,249	12,061,669
AECOM’s investment in joint ventures	138,056	138,067
Joint ventures summarized financial information
Revenue	16,139,622	16,105,498	14,378,461
Cost of revenue	14,922,909	15,021,157	13,432,996
Gross profit	1,216,713	1,084,341	945,465
Net income	636,187	460,255	$ 100,141
Equity Method Investment, Nonconsolidated Investee or Group of Investees
Joint Ventures and Variable Interest Entities [Line Items]
Current assets	1,537,700	1,379,000
Non-current assets	708,000	799,900
TOTAL ASSETS	2,245,700	2,178,900
Current liabilities	1,107,800	976,300
Non-current liabilities	92,400	114,800
TOTAL LIABILITIES	1,200,200	1,091,100
Joint ventures’ equity	1,045,500	1,087,800
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	2,245,700	2,178,900
AECOM’s investment in joint ventures	138,100	138,100
Joint ventures summarized financial information
Revenue	2,887,600	2,145,800
Cost of revenue	2,822,500	1,972,100
Gross profit	65,100	173,700
Net income	$ 67,100	$ 168,600

Schedule II: Valuation and Qualifying Accounts (Details) - SEC Schedule, 12-09, Allowance, Credit Loss - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	$ 87.9	$ 94.2	$ 104.0
Additions Charged to Cost of Revenue	18.3	30.9	40.9
Deductions	(20.6)	(38.7)	(50.8)
Other and Foreign Exchange Impact	(0.8)	1.5	0.1
Balance at the End of the Year	$ 84.8	$ 87.9	$ 94.2

Share-Based Payments - Schedule of Restricted Stock Units and PEP Units Activity (Details) - $ / shares shares in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Restricted Stock Units
Units
Outstanding at beginning (in units)	0.8	0.8	1.0
Granted (in units)	0.2	0.3	0.3
PEP units earned (unearned) (in units)	0.0	0.0	0.0
Vested (in units)	(0.2)	(0.3)	(0.4)
Cancelled (in units)	(0.1)	(0.0)	(0.1)
Outstanding at ending (in units)	0.7	0.8	0.8
Weighted Average Grant-Date Fair Value
Outstanding at beginning (in dollars per share)	$ 83.96	$ 68.34	$ 53.05
Granted (in dollars per share)	110.65	92.30	83.64
PEP units earned (unearned) (in dollars per share)	0	0	0
Vested (in dollars per share)	75.72	50.14	44.35
Cancelled (in dollars per share)	95.85	77.32	62.09
Outstanding at ending (in dollars per share)	$ 95.64	$ 83.96	$ 68.34
PEP Units
Units
Outstanding at beginning (in units)	0.7	0.7	0.7
Granted (in units)	0.2	0.2	0.2
PEP units earned (unearned) (in units)	0.1	0.2	0.2
Vested (in units)	(0.3)	(0.4)	(0.4)
Cancelled (in units)	(0.1)	0.0	0.0
Outstanding at ending (in units)	0.6	0.7	0.7
Weighted Average Grant-Date Fair Value
Outstanding at beginning (in dollars per share)	$ 95.38	$ 75.54	$ 60.60
Granted (in dollars per share)	129.28	104.66	94.64
PEP units earned (unearned) (in dollars per share)	85.46	52.50	43.19
Vested (in dollars per share)	85.46	52.50	43.19
Cancelled (in dollars per share)	109.53	89.76	71.71
Outstanding at ending (in dollars per share)	$ 109.74	$ 95.38	$ 75.54

Joint Ventures and Variable Interest Entities (Tables)

12 Months Ended

Sep. 30, 2025

Joint Ventures and Variable Interest Entities [Abstract]

Schedule of Financial Information of Consolidated Joint Ventures

Summary of financial information of the consolidated joint ventures was as follows:


	September 30, 2025		September 30, 2024

	(in millions)
Current assets	$	699.0	$	836.9
Non-current assets	84.4		83.1
Total assets	$	783.4	$	920.0

Current liabilities	$	591.4	$	763.6
Non-current liabilities	5.7		1.5
Total liabilities	597.1		765.1
Total AECOM deficit	(15.9)		(17.2)
Noncontrolling interests	202.2		172.1
Total owners’ equity	186.3		154.9
Total liabilities and owners’ equity	$	783.4	$	920.0

Schedule of Financial Information of Unconsolidated Joint Ventures

Summary of unaudited financial information of the unconsolidated joint ventures, as derived from their unaudited financial statements, was as follows:


	September 30, 2025		September 30, 2024

	(in millions)
Current assets	$	1,537.7	$	1,379.0
Non-current assets	708.0		799.9
Total assets	$	2,245.7	$	2,178.9

Current liabilities	$	1,107.8	$	976.3
Non-current liabilities	92.4		114.8
Total liabilities	1,200.2		1,091.1
Joint ventures’ equity	1,045.5		1,087.8
Total liabilities and joint ventures’ equity	$	2,245.7	$	2,178.9

AECOM’s investment in joint ventures	$	138.1	$	138.1


	Twelve Months Ended
	September 30, 2025		September 30, 2024

	(in millions)
Revenue	$	2,887.6	$	2,145.8
Cost of revenue	2,822.5		1,972.1
Gross profit	$	65.1	$	173.7
Net income	$	67.1	$	168.6

Summary of AECOM’s equity in earnings of unconsolidated joint ventures is as follows:


	Fiscal Year Ended
	September 30, 2025		September 30, 2024		September 30, 2023

	(in millions)
Pass-through joint ventures	$	27.6	$	29.0	$	24.5
Other joint ventures	(0.6)		(26.9)		(303.9)
Total	$	27.0	$	2.1	$	(279.4)

- Definition

Tabular disclosure of the significant judgments and assumptions made in determining whether a variable interest (as defined) held by the entity requires the variable interest entity (VIE) (as defined) to be consolidated and (or) disclose information about its involvement with the VIE, individually or in aggregate (as applicable); the nature of restrictions, if any, on the consolidated VIE's assets and on the settlement of its liabilities reported by an entity in its statement of financial position, including the carrying amounts of such assets and liabilities; the nature of, and changes in, the risks associated with involvement in the VIE; how involvement with the VIE affects the entity's financial position, financial performance, and cash flows; the lack of recourse if creditors (or beneficial interest holders) of the consolidated VIE have no recourse to the general credit of the primary beneficiary (if applicable); the terms of arrangements, giving consideration to both explicit arrangements and implicit variable interests, if any, that could require the entity to provide financial support to the VIE, including events or circumstances that could expose the entity to a loss; the methodology used by the entity for determining whether or not it is the primary beneficiary of the variable interest entity; the significant factors considered and judgments made in determining that the power to direct the activities of a VIE that most significantly impact the VIE's economic performance are shared (as defined); the carrying amounts and classification of assets and liabilities of the VIE included in the statement of financial position; the entity's maximum exposure to loss, if any, as a result of its involvement with the VIE, including how the maximum exposure is determined and significant sources of the entity's exposure to the VIE; a comparison of the carrying amounts of the assets and liabilities and the entity's maximum exposure to loss; information about any liquidity arrangements, guarantees, and (or) other commitments by third parties that may affect the fair value or risk of the entity's variable interest in the VIE; whether or not the entity has provided financial support or other support (explicitly or implicitly) to the VIE that it was not previously contractually required to provide or whether the entity intends to provide that support, including the type and amount of the support and the primary reasons for providing the support; and supplemental information the entity determines necessary to provide.

+ References + Details

Stockholders' Equity	12 Months Ended
Stockholders' Equity	Sep. 30, 2025
Stockholders' Equity Note [Abstract]
Stockholders' Equity	Stockholders’ Equity Common Stock Units—Common stock units are only redeemable for common stock. In the event of liquidation of the Company, holders of stock units are entitled to no greater rights than holders of common stock. See also Note 13.

- Definition

The entire disclosure for equity.

+ References

+ Details

Pension Benefit Obligations - Schedule of Amounts Recognized In the Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Amounts recognized in the consolidated balance sheets:
Pension benefit obligations	$ (133,193)	$ (172,360)
U.S.
Amounts recognized in the consolidated balance sheets:
Other non-current assets	0	0	$ 0
Accrued expenses and other current liabilities	(8,500)	(8,300)	(8,400)
Pension benefit obligations	(63,500)	(69,600)	(74,000)
Net amount recognized at end of year	(72,000)	(77,900)	(82,400)
Int’l
Amounts recognized in the consolidated balance sheets:
Other non-current assets	52,300	46,600	38,700
Accrued expenses and other current liabilities	0	0	0
Pension benefit obligations	(69,700)	(102,700)	(121,600)
Net amount recognized at end of year	$ (17,400)	$ (56,100)	$ (82,900)

- Definition

Amount of asset, recognized in statement of financial position, for overfunded defined benefit pension and other postretirement plans.

+ References + Details

Reportable Segments and Geographic Information - Schedule of Financial Information Concerning the Company's Reportable Segments (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Segment Reporting Information [Line Items]
Revenue	$ 16,139,622	$ 16,105,498	$ 14,378,461
Equity in earnings (losses) of joint ventures	27,013	2,124	(279,352)
Earnings before income taxes and amortization	1,181,300	1,046,400	642,400
Total
Segment Reporting Information [Line Items]
Revenue	16,139,600	16,105,500	14,378,500
Subcontractor and other direct costs	(8,566,800)	(8,940,500)	(7,675,700)
Employee compensation expense	(5,375,500)	(5,166,100)	(4,870,300)
Equity in earnings (losses) of joint ventures	27,000	2,100	(279,400)
Other segment items	(1,043,000)	(954,600)	(910,700)
Earnings before income taxes and amortization	1,181,300	1,046,400	642,400
Operating Segments \| Americas
Segment Reporting Information [Line Items]
Revenue	12,525,900	12,485,700	10,975,700
Subcontractor and other direct costs	(7,973,700)	(8,281,100)	(7,056,700)
Employee compensation expense	(3,089,400)	(2,929,000)	(2,729,900)
Equity in earnings (losses) of joint ventures	15,800	15,500	14,800
Other segment items	(609,700)	(514,900)	(482,300)
Earnings before income taxes and amortization	868,900	776,200	721,600
Operating Segments \| International
Segment Reporting Information [Line Items]
Revenue	3,613,200	3,618,400	3,402,100
Subcontractor and other direct costs	(593,100)	(659,400)	(619,000)
Employee compensation expense	(2,286,100)	(2,234,400)	(2,134,500)
Equity in earnings (losses) of joint ventures	11,800	13,500	9,700
Other segment items	(424,400)	(427,400)	(421,700)
Earnings before income taxes and amortization	321,400	310,700	236,600
Operating Segments \| AECOM Capital
Segment Reporting Information [Line Items]
Revenue	500	1,400	700
Subcontractor and other direct costs	0	0	0
Employee compensation expense	0	(2,700)	(5,900)
Equity in earnings (losses) of joint ventures	(600)	(26,900)	(303,900)
Other segment items	(8,900)	(12,300)	(6,700)
Earnings before income taxes and amortization	$ (9,000)	$ (40,500)	$ (315,800)

Reportable Segments and Geographic Information - Schedule of Reportable Segment (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Summarized financial information concerning the Company's reportable segments
Total assets	$ 12,200,249	$ 12,061,669
Investments in unconsolidated joint ventures	138,056	138,067
Depreciation and amortization	175,917	178,812	$ 175,725
Total
Summarized financial information concerning the Company's reportable segments
Total assets	12,200,200	12,061,700
Investments in unconsolidated joint ventures	138,100	138,100
Depreciation and amortization	(175,900)	(178,800)	(175,700)
Operating Segments \| Americas
Summarized financial information concerning the Company's reportable segments
Total assets	7,866,900	7,988,100
Investments in unconsolidated joint ventures	44,000	34,100
Depreciation and amortization	(94,300)	(101,600)	(100,600)
Operating Segments \| International
Summarized financial information concerning the Company's reportable segments
Total assets	2,702,900	2,734,500
Investments in unconsolidated joint ventures	56,600	61,100
Depreciation and amortization	(70,800)	(67,200)	(67,200)
Operating Segments \| AECOM Capital
Summarized financial information concerning the Company's reportable segments
Total assets	41,600	53,200
Investments in unconsolidated joint ventures	37,500	42,900
Depreciation and amortization	0	0	0
Corporate and Assets Held for Sale
Summarized financial information concerning the Company's reportable segments
Total assets	1,588,800	1,285,900
Investments in unconsolidated joint ventures	0	0
Depreciation and amortization	$ (10,800)	$ (10,000)	$ (7,900)

Debt - 2027 and 2033 Senior Notes (Details) - USD ($)		1 Months Ended
Debt - 2027 and 2033 Senior Notes (Details) - USD ($)	Jul. 22, 2025	Aug. 31, 2025	Sep. 30, 2025	Jul. 31, 2025	Feb. 21, 2017
2027 Senior Notes
Debt Instrument [Line Items]
Aggregate principal amount					$ 1,000,000,000
Interest rate (as percent)					5.125%
Repurchased face amount				$ 732,914,000
Make-whole payment		$ 9,100,000
2033 Senior Notes \| Senior Notes
Debt Instrument [Line Items]
Aggregate principal amount	$ 1,200,000,000
Interest rate (as percent)	6.00%
Estimated fair value			$ 1,227,000,000
2033 Senior Notes \| Senior Notes \| Debt Instrument, Redemption, Period One
Debt Instrument [Line Items]
Redemption price, percentage of principal amount redeemed	100.00%
2033 Senior Notes \| Senior Notes \| Debt Instrument, Redemption, Period Two
Debt Instrument [Line Items]
Redemption price, percentage of principal amount redeemed	40.00%
2033 Senior Notes \| Senior Notes \| Debt Instrument, Redemption, Period Three
Debt Instrument [Line Items]
Redemption price, percentage of principal amount redeemed	106.00%
2033 Senior Notes \| Senior Notes \| Debt Instrument, Redemption, Period Four
Debt Instrument [Line Items]
Redemption price (as percent)	103.00%
2033 Senior Notes \| Senior Notes \| Debt Instrument, Redemption, Period Five
Debt Instrument [Line Items]
Redemption price (as percent)	101.50%
2033 Senior Notes \| Senior Notes \| Debt Instrument, Redemption, Period After Five Years
Debt Instrument [Line Items]
Redemption price (as percent)	100.00%

Leases - Schedule of Additional Cash Flow Information Related to Leases (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$ 172.6	$ 184.9	$ 188.3
Operating cash flows from finance leases	3.7	3.0	2.5
Financing cash flows from finance leases	32.4	28.9	23.7
Right-of-use assets obtained in exchange for new operating leases	130.9	90.1	96.6
Right-of-use assets obtained in exchange for new finance leases	$ 47.2	$ 26.6	$ 37.5

Discontinued Operations, Goodwill and Intangible Assets - Schedule of Balance Sheet Information of Assets and Liabilities Held for Sale (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Sep. 30, 2024
Disposal Group, Including Discontinued Operation, Balance Sheet Disclosures [Abstract]
Non-current assets held for sale	$ 18,953	$ 0
Held for Sale
Disposal Group, Including Discontinued Operation, Balance Sheet Disclosures [Abstract]
Cash and cash equivalents	0	4,000
Receivables and contract assets	0	73,200
Current assets held for sale	0	77,200
Investment in unconsolidated joint venture	18,900	0
Property and equipment, net	0	16,700
Other	100	1,200
Write-down of assets to fair value less cost to sell	0	(17,900)
Non-current assets held for sale	19,000	0
Accounts payable and accrued expenses	0	35,600
Current liabilities held for sale	0	35,600
Long-term liabilities held for sale	$ 0	$ 0

Commitments and Contingencies	12 Months Ended
Commitments and Contingencies	Sep. 30, 2025
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies The Company records amounts representing its probable estimated liabilities relating to claims, guarantees, litigation, audits and investigations. The Company relies in part on qualified actuaries to assist it in determining the level of reserves to establish for insurance-related claims that are known and have been asserted against it, and for insurance-related claims that are believed to have been incurred based on actuarial analysis, but have not yet been reported to the Company’s claims administrators as of the respective balance sheet dates. The Company includes any adjustments to such insurance reserves in its consolidated results of operations. The Company’s reasonably possible loss disclosures are presented on a gross basis prior to the consideration of insurance recoveries. The Company does not record gain contingencies until they are realized. In the ordinary course of business, the Company may not be aware that it or its affiliates are under investigation and may not be aware of whether or not a known investigation has been concluded. In the ordinary course of business, the Company may enter into various arrangements providing financial or performance assurance to clients, lenders, or partners. Such arrangements include standby letters of credit, surety bonds, and corporate guarantees to support the creditworthiness or the project execution commitments of its affiliates, partnerships and joint ventures. The Company’s unsecured credit arrangements are used for standby letters of credit issued in connection with general and professional liability insurance programs and for contract performance guarantees. At September 30, 2025 and 2024, these outstanding standby letters of credit totaled $899.4 million and $934.5 million, respectively. As of September 30, 2025, the Company had $367.4 available under these unsecured credit facilities. Performance arrangements typically have various expiration dates ranging from the completion of the project contract and extending beyond contract completion in some circumstances such as for warranties. The Company may also guarantee that a project, when complete, will achieve specified performance standards. If the project subsequently fails to meet guaranteed performance standards, the Company may incur additional costs, pay liquidated damages or be held responsible for the costs incurred by the client to achieve the required performance standards. The potential payment amount of an outstanding performance arrangement is typically the remaining cost of work to be performed by or on behalf of third parties. Generally, under joint venture arrangements, if a partner is financially unable to complete its share of the contract, the other partner(s) may be required to complete those activities. At September 30, 2025, the Company was contingently liable in the amount of approximately $903.8 million in issued standby letters of credit and $5.6 billion in issued surety bonds primarily to support project execution. In the ordinary course of business, the Company enters into various agreements providing financial or performance assurances to clients on behalf of certain unconsolidated partnerships, joint ventures and other jointly executed contracts. These agreements are entered into primarily to support the project execution commitments of these entities. The Company’s investment adviser jointly manages and sponsors the AECOM-Canyon Equity Fund, L.P. (the “Fund”), in which the Company indirectly holds an equity interest and has an ongoing capital commitment to fund investments. At September 30, 2025, the Company has capital commitments of $5.1 million to the Fund over the next three years In addition, in connection with the investment activities of AECOM Capital, the Company provides guarantees of certain contractual obligations, including guarantees for completion of projects, limited debt repayment, environmental indemnity obligations and other lender required guarantees. In February 2024, the Company was informed of a potential liability as one of the indemnitors on a divested business’ surety bonds. The Company does not have sufficient information to determine the range of potential impacts; however, it is reasonably possible that the Company may incur additional costs related to these bonds. In connection with the resolution of contingencies related to the sale of the civil infrastructure construction business, the Company agreed to act as an additional guarantor on the counterparty’s existing debt, which was extended to March 2028.

Income Taxes - Schedule of Reconciliation of Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024
Unrecognized Tax Benefits [Roll Forward]
Balance at the beginning of the year	$ 81.3	$ 62.1
Gross increase in current period’s tax positions	9.2	34.5
Gross increase in prior years’ tax positions	47.0	13.9
Gross decrease in prior years’ tax positions	(6.4)	(20.1)
Decrease due to settlement with tax authorities	0.0	(7.4)
Decrease due to lapse of statute of limitations	(1.3)	(2.2)
Gross change due to foreign exchange fluctuations	(0.2)
Gross change due to foreign exchange fluctuations		0.5
Balance at the end of the year	$ 129.6	$ 81.3

Pension Benefit Obligations - Schedule of Additional Year-End Information for Pension Plans With Accumulated Benefit Obligations In Excess of Plan Assets (Details) - USD ($) $ in Millions	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
U.S.
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	$ 165.8	$ 175.1	$ 168.8
Accumulated benefit obligation	165.8	175.1	168.8
Fair value of plan assets	104.9	109.0	98.8
Int’l
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	395.6	649.8	628.1
Accumulated benefit obligation	395.6	649.8	628.1
Fair value of plan assets	$ 325.9	$ 547.1	$ 506.5

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

Discontinued Operations, Goodwill and Intangible Assets - Schedule of Estimated Amortization Expense of Intangible Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Sep. 30, 2024
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2026	$ 37,200
2027	37,200
2028	37,200
2029	36,000
2030	35,700
Total	$ 183,284	$ 6,932

Significant Accounting Policies (Details)	12 Months Ended
Significant Accounting Policies (Details)	Sep. 30, 2025
Accounting Policies [Abstract]
Market-related valuation calculation period (in years)	5 years
Net unrecognized gain (loss) threshold subject to amortization (in percent)	10.00%
Minimum \| Building
Property and equipment
Estimated useful live (in years)	10 years
Minimum \| Furniture and fixtures
Property and equipment
Estimated useful live (in years)	3 years
Minimum \| Computer systems and equipment
Property and equipment
Estimated useful live (in years)	3 years
Maximum \| Building
Property and equipment
Estimated useful live (in years)	45 years
Maximum \| Furniture and fixtures
Property and equipment
Estimated useful live (in years)	10 years
Maximum \| Computer systems and equipment
Property and equipment
Estimated useful live (in years)	12 years

Joint Ventures and Variable Interest Entities - Schedule of Equity in Earnings of Unconsolidated Joint Ventures (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Joint Ventures and Variable Interest Entities [Line Items]
Total	$ 27,013	$ 2,124	$ (279,352)
Unconsolidated Joint Ventures
Joint Ventures and Variable Interest Entities [Line Items]
Total	27,000	2,100	(279,400)
Unconsolidated Joint Ventures \| Pass-through joint ventures
Joint Ventures and Variable Interest Entities [Line Items]
Total	27,600	29,000	24,500
Unconsolidated Joint Ventures \| Other joint ventures
Joint Ventures and Variable Interest Entities [Line Items]
Total	$ (600)	$ (26,900)	$ (303,900)

- Definition

Amount of income (loss) for proportionate share of equity method investee's income (loss).

+ References + Details

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References + Details

Revenue Recognition - Schedule of Net Accounts Receivable (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Sep. 30, 2024
Revenue from Contract with Customer [Abstract]
Billed	$ 1,934,300	$ 2,184,900
Contract retentions	647,600	696,300
Total accounts receivable—gross	2,581,900	2,881,200
Allowance for doubtful accounts and credit losses	(84,800)	(87,900)
Total accounts receivable—net	$ 2,497,147	$ 2,793,307

Commitments and Contingencies (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024
Fund Investment Capital
Loss Contingencies [Line Items]
Capital commitments	$ 5.1
Commitment period (in years)	3 years
Standby Letters of Credit
Loss Contingencies [Line Items]
Outstanding standby letters of credit	$ 899.4	$ 934.5
Amount available under unsecured credit facilities	367.4
Contingently liable for issuance of standby letters of credit and surety bonds	903.8
Surety Bond
Loss Contingencies [Line Items]
Contingently liable for issuance of standby letters of credit and surety bonds	$ 5,600.0

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 275
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-9

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 450
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483076/450-20-50-4

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 450
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483076/450-20-50-9

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 720
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483359/720-20-50-1

Reference 5: http://www.xbrl.org/2003/role/exampleRef
-Topic 460
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 27
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482395/460-10-55-27

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 450
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483076/450-20-50-9

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 450
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483076/450-20-50-4

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 460
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482425/460-10-50-3

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 450
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483076/450-20-50-1

+ Details

Pension Benefit Obligations - Schedule of Fair Values of Pension Plan Assets By Major Asset Categories (Details) - USD ($) $ in Millions	Sep. 30, 2025	Sep. 30, 2024
Defined Benefit Plan Disclosure [Line Items]
Total		$ 913.3
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Total		22.1
Debt securities
Defined Benefit Plan Disclosure [Line Items]
Total	$ 0.0	391.5
Diversified and equity funds
Defined Benefit Plan Disclosure [Line Items]
Total		286.7
Fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Total		213.9
Absolute return fund
Defined Benefit Plan Disclosure [Line Items]
Total		5.9
Derivative instruments and other
Defined Benefit Plan Disclosure [Line Items]
Total		(6.8)
Fair Value, Inputs, Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Total	876.8
Fair Value, Inputs, Level 1, 2 and 3 \| Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Total	20.5
Fair Value, Inputs, Level 1, 2 and 3 \| Debt securities
Defined Benefit Plan Disclosure [Line Items]
Total	361.4
Fair Value, Inputs, Level 1, 2 and 3 \| Diversified and equity funds
Defined Benefit Plan Disclosure [Line Items]
Total	272.5
Fair Value, Inputs, Level 1, 2 and 3 \| Fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Total	220.5
Fair Value, Inputs, Level 1, 2 and 3 \| Absolute return fund
Defined Benefit Plan Disclosure [Line Items]
Total	5.1
Fair Value, Inputs, Level 1, 2 and 3 \| Derivative instruments and other
Defined Benefit Plan Disclosure [Line Items]
Total	(3.2)
Quoted Prices in Active Markets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Total	486.0	487.6
Quoted Prices in Active Markets (Level 1) \| Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Total	20.5	22.1
Quoted Prices in Active Markets (Level 1) \| Debt securities
Defined Benefit Plan Disclosure [Line Items]
Total	361.4	391.5
Quoted Prices in Active Markets (Level 1) \| Diversified and equity funds
Defined Benefit Plan Disclosure [Line Items]
Total	71.5	48.5
Quoted Prices in Active Markets (Level 1) \| Fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Total	22.7	17.3
Quoted Prices in Active Markets (Level 1) \| Absolute return fund
Defined Benefit Plan Disclosure [Line Items]
Total	0.0	0.0
Quoted Prices in Active Markets (Level 1) \| Derivative instruments and other
Defined Benefit Plan Disclosure [Line Items]
Total	9.9	8.2
Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Total	5.4	2.6
Significant Other Observable Inputs (Level 2) \| Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Total	0.0	0.0
Significant Other Observable Inputs (Level 2) \| Debt securities
Defined Benefit Plan Disclosure [Line Items]
Total	0.0	0.0
Significant Other Observable Inputs (Level 2) \| Diversified and equity funds
Defined Benefit Plan Disclosure [Line Items]
Total	14.1	13.5
Significant Other Observable Inputs (Level 2) \| Fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Total	4.4	4.1
Significant Other Observable Inputs (Level 2) \| Absolute return fund
Defined Benefit Plan Disclosure [Line Items]
Total	0.0	0.0
Significant Other Observable Inputs (Level 2) \| Derivative instruments and other
Defined Benefit Plan Disclosure [Line Items]
Total	(13.1)	(15.0)
Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Total	0.0	0.0
Significant Unobservable Inputs (Level 3) \| Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Total	0.0	0.0
Significant Unobservable Inputs (Level 3) \| Debt securities
Defined Benefit Plan Disclosure [Line Items]
Total	0.0	0.0
Significant Unobservable Inputs (Level 3) \| Diversified and equity funds
Defined Benefit Plan Disclosure [Line Items]
Total	0.0	0.0
Significant Unobservable Inputs (Level 3) \| Fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Total	0.0	0.0
Significant Unobservable Inputs (Level 3) \| Absolute return fund
Defined Benefit Plan Disclosure [Line Items]
Total	0.0	0.0
Significant Unobservable Inputs (Level 3) \| Derivative instruments and other
Defined Benefit Plan Disclosure [Line Items]
Total	0.0	0.0
Investments measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Total	385.4	423.1
Investments measured at NAV \| Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Total	0.0	0.0
Investments measured at NAV \| Debt securities
Defined Benefit Plan Disclosure [Line Items]
Total		0.0
Investments measured at NAV \| Diversified and equity funds
Defined Benefit Plan Disclosure [Line Items]
Total	186.9	224.7
Investments measured at NAV \| Fixed income funds
Defined Benefit Plan Disclosure [Line Items]
Total	193.4	192.5
Investments measured at NAV \| Absolute return fund
Defined Benefit Plan Disclosure [Line Items]
Total	5.1	5.9
Investments measured at NAV \| Derivative instruments and other
Defined Benefit Plan Disclosure [Line Items]
Total	$ 0.0	$ 0.0

Income Taxes - Schedule of Deferred Tax Assets (liabilities) (Details) - USD ($) $ in Millions	Sep. 30, 2025	Sep. 30, 2024
Deferred tax assets:
Compensation and benefit accruals not currently deductible	$ 81.8	$ 85.4
Net operating loss carryforwards	99.2	107.5
Self-insurance reserves	66.6	38.3
Research and experimentation and other tax credits	34.3	67.1
Pension liability	23.5	34.9
Accrued liabilities	263.3	265.7
Capital loss carryforward	13.0	49.5
Partnership investment	15.5	22.3
Other	12.2	8.2
Total deferred tax assets	609.4	678.9
Deferred tax liabilities:
Unearned revenue	(31.0)	(4.1)
Depreciation and amortization	(58.9)	(83.7)
Acquired intangible assets	(39.6)	0.0
Investment in subsidiaries	(9.8)	(9.9)
Right of use assets	(82.4)	(85.2)
Contingent consideration	0.0	(30.5)
Other	(3.3)	(5.4)
Total deferred tax liabilities	(225.0)	(218.8)
Valuation allowance	(157.1)	(160.9)
Net deferred tax assets	$ 227.3	$ 299.2

Pension Benefit Obligations - Schedule of Expected Future Benefit Payments (Details) $ in Millions	Sep. 30, 2025 USD ($)
U.S.
Defined Benefit Plan Disclosure [Line Items]
2026	$ 26.8
2027	18.3
2028	17.6
2029	16.6
2030	15.7
2031-2035	66.0
Total	161.0
Int’l
Defined Benefit Plan Disclosure [Line Items]
2026	52.2
2027	51.3
2028	52.9
2029	54.8
2030	56.0
2031-2035	297.5
Total	$ 564.7

Pension Benefit Obligations - Schedule of Amounts Included In Accumulated Other Comprehensive Loss Expected to Be Recognized as Components of Net Periodic Benefit Cost (Details) $ in Millions	Sep. 30, 2025 USD ($)
U.S.
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service cost	$ 0.0
Amortization of net actuarial (losses) gain	(3.8)
Total	(3.8)
Int’l
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service cost	(0.1)
Amortization of net actuarial (losses) gain	0.6
Total	$ 0.5

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

Pension Benefit Obligations

12 Months Ended

Sep. 30, 2025

Retirement Benefits [Abstract]

Pension Benefit Obligations

In the U.S., the Company sponsors various qualified defined benefit pension plans. Benefits under these plans generally are based on the employee’s years of creditable service and compensation; however, all U.S. defined benefit plans are closed to new participants and have frozen accruals.

The Company also sponsors various non-qualified plans in the U.S.; all of these plans are frozen. Outside the U.S., the Company sponsors various pension plans, which are appropriate to the country in which the Company operates, some of which are government mandated.

The following tables provide reconciliations of the changes in the U.S. and international plans’ benefit obligations, reconciliations of the changes in the fair value of assets for the last three years ended September 30, and reconciliations of the funded status as of September 30 of each year.


	Fiscal Year Ended
	September 30, 2025				September 30, 2024				September 30, 2023
	U.S.		Int’l		U.S.		Int’l		U.S.		Int’l

	(in millions)
Change in benefit obligation:
Benefit obligation at beginning of year	$	186.9	$	860.4	$	181.2	$	756.2	$	198.1	$	791.2
Service cost	—		0.2		—		0.2		—		0.3
Participant contributions	0.1		0.2		0.1		0.3		0.1		0.2
Interest cost	7.9		40.1		9.7		43.7		9.8		47.7
Benefits and expenses paid	(17.1)		(46.2)		(17.6)		(47.7)		(17.2)		(42.2)
Actuarial loss (gain)	(0.2)		(69.8)		13.5		37.0		(8.8)		(112.5)
Plan settlements	(0.7)		—		—		(3.2)		(1.5)		(1.5)
Transfers in	—		—		—		—		0.7		—
Foreign currency translation loss	—		4.4		—		73.9		—		73.0
Benefit obligation at end of year	$	176.9	$	789.3	$	186.9	$	860.4	$	181.2	$	756.2


	Fiscal Year Ended
	September 30, 2025				September 30, 2024				September 30, 2023
	U.S.		Int’l		U.S.		Int’l		U.S.		Int’l

	(in millions)
Change in plan assets
Fair value of plan assets at beginning of year	$	109.0	$	804.3	$	98.8	$	673.3	$	101.4	$	683.5
Actual return on plan assets	3.0		(15.1)		15.8		89.0		7.8		(54.2)
Employer contributions	10.6		23.7		11.9		25.1		8.2		24.8
Participant contributions	0.1		0.2		0.1		0.3		0.1		0.2
Benefits and expenses paid	(17.1)		(46.2)		(17.6)		(47.7)		(17.2)		(42.2)
Plan settlements	(0.7)		—		—		(3.2)		(1.5)		(1.5)
Foreign currency translation gain	—		5.0		—		67.5		—		62.7
Fair value of plan assets at end of year	$	104.9	$	771.9	$	109.0	$	804.3	$	98.8	$	673.3


	Fiscal Year Ended
	September 30, 2025				September 30, 2024				September 30, 2023
	U.S.		Int’l		U.S.		Int’l		U.S.		Int’l

	(in millions)
Reconciliation of funded status:
Funded status at end of year	$	(72.0)	$	(17.4)	$	(77.9)	$	(56.1)	$	(82.4)	$	(82.9)
Contribution made after measurement date	N/A		N/A		N/A		N/A		N/A		N/A
Net amount recognized at end of year	$	(72.0)	$	(17.4)	$	(77.9)	$	(56.1)	$	(82.4)	$	(82.9)

The following table sets forth the amounts recognized in the consolidated balance sheets as of September 30, 2025, 2024 and 2023:


	Fiscal Year Ended
	September 30, 2025				September 30, 2024				September 30, 2023
	U.S.		Int’l		U.S.		Int’l		U.S.		Int’l

	(in millions)
Amounts recognized in the consolidated balance sheets:
Other non-current assets	$	—	$	52.3	$	—	$	46.6	$	—	$	38.7
Accrued expenses and other current liabilities	(8.5)		—		(8.3)		—		(8.4)		—
Pension benefit obligations	(63.5)		(69.7)		(69.6)		(102.7)		(74.0)		(121.6)
Net amount recognized in the balance sheet	$	(72.0)	$	(17.4)	$	(77.9)	$	(56.1)	$	(82.4)	$	(82.9)

The following table details the reconciliation of amounts in the consolidated statements of stockholders’ equity for the fiscal years ended September 30, 2025, 2024 and 2023:


	Fiscal Year Ended
	September 30, 2025				September 30, 2024				September 30, 2023
	U.S.		Int’l		U.S.		Int’l		U.S.		Int’l

	(in millions)
Reconciliation of amounts in consolidated statements of stockholders’ equity:
Prior service cost	$	(0.1)	$	(1.2)	$	(0.1)	$	(1.3)	$	(0.1)	$	(1.2)
Net loss	(75.4)		(235.5)		(77.6)		(234.9)		(77.5)		(207.1)
Total recognized in accumulated other comprehensive loss	$	(75.5)	$	(236.7)	$	(77.7)	$	(236.2)	$	(77.6)	$	(208.3)

The components of net periodic benefit cost other than the service cost component are included in other income in the consolidated statement of operations. The following table details the components of net periodic benefit cost for the Company’s pension plans for fiscal years ended September 30, 2025, 2024 and 2023:


	Fiscal Year Ended
	September 30, 2025				September 30, 2024				September 30, 2023
	U.S.		Int’l		U.S.		Int’l		U.S.		Int’l

	(in millions)
Components of net periodic benefit cost:
Service costs	$	—	$	0.2	$	—	$	0.2	$	—	$	0.3
Interest cost on projected benefit obligation	7.9		40.1		9.7		43.7		9.8		47.7
Expected return on plan assets	(4.8)		(52.2)		(5.5)		(57.4)		(5.8)		(60.8)
Amortization of prior service costs	—		0.1		—		0.1		—		0.1
Amortization of net loss (gain)	3.7		(1.3)		3.1		(2.3)		3.5		(0.6)
Settlement loss (gain) recognized	0.1		—		—		0.1		(0.1)		0.2
Net periodic benefit cost (credit)	$	6.9	$	(13.1)	$	7.3	$	(15.6)	$	7.4	$	(13.1)

The amount of applicable deferred income taxes included in other comprehensive income arising from a change in net prior service cost and net gain/loss was $1.1 million, $2.1 million, and $3.1 million in the years ended September 30, 2025, 2024 and 2023, respectively.

Amounts included in accumulated other comprehensive loss as of September 30, 2025 that are expected to be recognized as components of net periodic benefit cost during fiscal 2026 are (in millions):


	U.S.		Int’l
Amortization of prior service cost	$	—	$	(0.1)
Amortization of net actuarial (losses) gain	(3.8)		0.6
Total	$	(3.8)	$	0.5

The table below provides additional year-end information for pension plans with accumulated benefit obligations in excess of plan assets.


	Fiscal Year Ended
	September 30, 2025				September 30, 2024				September 30, 2023
	U.S.		Int’l		U.S.		Int’l		U.S.		Int’l

	(in millions)
Projected benefit obligation	$	165.8	$	395.6	$	175.1	$	649.8	$	168.8	$	628.1
Accumulated benefit obligation	$	165.8	$	395.6	$	175.1	$	649.8	$	168.8	$	628.1
Fair value of plan assets	$	104.9	$	325.9	$	109.0	$	547.1	$	98.8	$	506.5

Funding requirements for each pension plan are determined based on the local laws of the country where such pension plan resides. In certain countries, the funding requirements are mandatory while in other countries, they are discretionary. The Company currently intends to contribute $25.0 million to the international plans in fiscal 2026. The required minimum contributions for U.S. plans are not significant. In addition, the Company may make discretionary contributions. The Company currently intends to contribute $10.8 million to U.S. plans in fiscal 2026.

The table below provides the expected future benefit payments, in millions:


Year Ending September 30,	U.S.		Int’l
2026	$	26.8	$	52.2
2027	18.3		51.3
2028	17.6		52.9
2029	16.6		54.8
2030	15.7		56.0
2031-2035	66.0		297.5
Total	$	161.0	$	564.7

The underlying assumptions for the pension plans are as follows:


	Fiscal Year Ended
	September 30, 2025				September 30, 2024				September 30, 2023
	U.S.		Int’l		U.S.		Int’l		U.S.		Int’l

	(in millions)
Weighted-average assumptions to determine benefit obligation:
Discount rate	5.01	%	5.83	%	4.73	%	5.04	%	5.76	%	5.65	%
Salary increase rate	N/A		2.81	%	N/A		2.91	%	N/A		3.06	%
Weighted-average assumptions to determine net periodic benefit cost:
Discount rate	4.73	%	5.04	%	5.76	%	5.65	%	5.40	%	5.27	%
Salary increase rate	N/A		2.91	%	N/A		3.06	%	N/A		3.48	%
Expected long-term rate of return on plan assets	6.25	%	5.51	%	6.90	%	5.74	%	7.00	%	6.04	%

Pension costs are determined using the assumptions as of the beginning of the plan year. The funded status is determined using the assumptions as of the end of the plan year.

The following table summarizes the Company’s target allocation for 2025 and pension plan asset allocation, both U.S. and International, as of September 30, 2025 and 2024:


					Percentage of Plan Assets as of September 30,
	Target Allocations				2025				2024
	U.S.		Int’l		U.S.		Int’l		U.S.		Int’l
Asset Category:
Equities	18	%	25	%	19	%	24	%	24	%	25	%
Debt	78		65		74		64		67		64
Cash	—		3		2		2		4		2
Diversified and other	4		7		5		10		5		9
Total	100	%	100	%	100	%	100	%	100	%	100	%

The Company’s domestic and foreign plans seek a competitive rate of return relative to an appropriate level of risk depending on the funded status and obligations of each plan and typically employ both active and passive investment management strategies. The Company’s risk management practices include diversification across asset classes and investment styles and periodic rebalancing toward asset allocation targets. The target asset allocation selected for each plan reflects a risk/return profile that the Company believes is appropriate relative to each plan’s liability structure and return goals.

To develop the expected long-term rate of return on assets assumption, the Company considered the historical returns and the future expectations for returns for each asset class, as well as the target asset allocation of the pension portfolio and the diversification of the portfolio. This resulted in the selection of a 6.25% and 5.51% weighted-average long-term rate of return on assets assumption for the fiscal year ended September 30, 2025 for U.S. and non-U.S. plans, respectively.

As of September 30, 2025, the fair values of the Company’s pension plan assets by major asset categories were as follows:


			Fair Value Measurement as of September 30, 2025
	Total Carrying Value as of September 30, 2025		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Investments measured at NAV

	(in millions)
Cash and cash equivalents	$	20.5	$	20.5	$	—	$	—	$	—
Debt securities	361.4		361.4		—		—		—
Investment funds:
Diversified and equity funds	272.5		71.5		14.1		—		186.9
Fixed income funds	220.5		22.7		4.4		—		193.4
Absolute return fund	5.1		—		—		—		5.1
Derivative instruments and other	(3.2)		9.9		(13.1)		—		—
Total	$	876.8	$	486.0	$	5.4	$	—	$	385.4

As of September 30, 2024, the fair values of the Company’s pension plan assets by major asset categories were as follows:


			Fair Value Measurement as of September 30, 2024
	Total Carrying Value as of September 30, 2024		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Investments measured at NAV

	(in millions)
Cash and cash equivalents	$	22.1	$	22.1	$	—	$	—	$	—
Debt securities	391.5		391.5		—		—		—
Investment funds:
Diversified and equity funds	286.7		48.5		13.5		—		224.7
Fixed income funds	213.9		17.3		4.1		—		192.5
Absolute return fund	5.9		—		—		—		5.9
Derivative instruments and other	(6.8)		8.2		(15.0)		—		—
Total	$	913.3	$	487.6	$	2.6	$	—	$	423.1

Cash equivalents are mostly comprised of short-term money-market instruments and are valued at cost, which approximates fair value.

For investment funds not traded on an active exchange, or if the closing price is not available, the trustee obtains indicative quotes from a pricing vendor, broker, or investment manager. These funds are categorized as Level 2 if the custodian obtains corroborated quotes from a pricing vendor or categorized as Level 3 if the custodian obtains uncorroborated quotes from a broker or investment manager.

Fixed income investment funds, not traded on an active exchange, categorized as Level 2 are valued by the trustee using pricing models that use verifiable observable market data (e.g., interest rates and yield curves observable at commonly quoted intervals), bids provided by brokers or dealers, or quoted prices of securities with similar characteristics.

Common collective investment funds are valued based on net asset value (NAV) per share or unit as a practical expedient as reported by the fund manager, multiplied by the number of shares or units held as of the measurement date. Accordingly, these NAV-based investments have been excluded from the fair value hierarchy. These collective investment funds have redemption notice periods and are redeemable at the NAV, less transaction fees. There are no significant unfunded commitments related to these investments.

Multiemployer Pension Plans

The Company participates in construction-industry multiemployer pension plans. Generally, the plans provide defined benefits to substantially all employees covered by collective bargaining agreements. Under the Employee Retirement Income Security Act, a contributor to a multiemployer plan is liable, upon termination or withdrawal from a plan, for its proportionate share of a plan’s unfunded vested liability. The Company’s aggregate contributions to these multiemployer plans were $2.7 million and $2.5 million for the years ended September 30, 2025 and 2024, respectively. At September 30, 2025 and 2024, none of the plans in which the Company participates are individually significant to its consolidated financial statements.

- Definition

The entire disclosure for retirement benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
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+ Details

Insider Trading Arrangements

3 Months Ended

Sep. 30, 2025

Trading Arrangements, by Individual

Material Terms of Trading Arrangement

Name and Title

Date of Adoption of

Rule 10b5-1 Trading Plan

Scheduled Expiration
Date of Rule 10b5-1
Trading Plan

Aggregate Number of
Securities to Be
Purchased or Sold

Lara Poloni, President

9/11/2025

12/31/2025

Sale of (i) the number of shares of common stock resulting from the vesting of 10,040 restricted stock awards and accrued dividend equivalents and (ii) the number of shares of common stock resulting from the vesting of Performance Earning Program awards (15,060 shares of common stock at target performance) and accrued dividend equivalents

David Gan,

Chief Legal Officer

8/14/2025

02/09/2026

Sale of (i) 6,000 shares of common stock, (ii) the number of shares of common stock resulting from the vesting of 5,976 restricted stock awards and accrued dividend equivalents and (iii) the number of shares of common stock resulting from the vesting of Performance Earning Program awards (8,964 shares of common stock at target performance) and accrued dividend equivalents

Non-Rule 10b5-1 Arrangement Adopted

false

Rule 10b5-1 Arrangement Terminated

false

Non-Rule 10b5-1 Arrangement Terminated

false

David Gan [Member]

Trading Arrangements, by Individual

Name

David Gan

Title

Chief Legal Officer

Rule 10b5-1 Arrangement Adopted

true

8/14/2025

02/09/2026

179 days

Trading Arrangements, by Individual

Name

Lara Poloni

Title

President

Rule 10b5-1 Arrangement Adopted

true

Adoption Date

9/11/2025

Expiration Date

12/31/2025

Arrangement Duration

111 days

Lara Poloni Trading Arrangement, Vesting Of Restricted Stock Awards [Member] | Lara Poloni [Member]

Trading Arrangements, by Individual

Aggregate Available

10,040

Lara Poloni Trading Arrangement, Common Stock At Target Performance [Member] | Lara Poloni [Member]

Trading Arrangements, by Individual

Aggregate Available

15,060

David Gan Trading Arrangement, Common Stock [Member] | David Gan [Member]

Trading Arrangements, by Individual

Aggregate Available

6,000

David Gan Trading Arrangement, Vesting Of Restricted Stock Awards [Member] | David Gan [Member]

Trading Arrangements, by Individual

Aggregate Available

5,976

David Gan Trading Arrangement, Common Stock At Target Performance [Member] | David Gan [Member]

Trading Arrangements, by Individual

Aggregate Available

8,964

Discontinued Operations, Goodwill and Intangible Assets - Schedule of Income Statement Information of Discontinued Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Loss on disposal activities	$ 0	$ (90,412)	$ (43,222)
Net loss from discontinued operations	(75,364)	(104,997)	(57,207)
Held for Sale
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Revenue	97,600	178,200	212,800
Cost of revenue	101,400	181,100	223,200
Gross loss	(3,800)	(2,900)	(10,400)
Equity in losses of joint ventures	(10,100)	(3,400)	(2,900)
Loss on disposal activities	(83,800)	(97,100)	(50,600)
Transaction costs	0	(200)	(200)
Loss from operations	(97,700)	(103,600)	(64,100)
Other expense	(300)	(1,500)	(1,000)
Loss before taxes	(98,000)	(105,100)	(65,100)
Income tax benefit	(22,600)	(100)	(7,900)
Net loss from discontinued operations	$ (75,400)	$ (105,000)	$ (57,200)

Discontinued Operations, Goodwill and Intangible Assets - Schedule of Gross Amount and Accumulated Amortization of Acquired Identifiable Intangible Assets with Finite Useful Lives (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Sep. 30, 2024
Discontinued Operations, Goodwill and Intangible Assets
Gross Amount	$ 185,800	$ 671,700
Accumulated Amortization	(2,500)	(664,800)
Total	183,284	6,932
Backlog and Customer relationships
Discontinued Operations, Goodwill and Intangible Assets
Gross Amount	7,400	671,700
Accumulated Amortization	(2,500)	(664,800)
Total	$ 4,900	6,900
Backlog and Customer relationships \| Minimum
Discontinued Operations, Goodwill and Intangible Assets
Amortization Period (in years)	1 year
Backlog and Customer relationships \| Maximum
Discontinued Operations, Goodwill and Intangible Assets
Amortization Period (in years)	11 years
Intellectual property
Discontinued Operations, Goodwill and Intangible Assets
Gross Amount	$ 178,400	0
Accumulated Amortization	0	0
Total	$ 178,400	$ 0
Amortization Period (in years)	5 years

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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+ Details

Share-Based Payments - Narrative (Details) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Compensation expense under defined contribution plans	$ 26.0	$ 24.7	$ 23.1
Compensation expense related to share-based payments	61.4	61.5	$ 45.9
Unrecognized compensation expense	$ 106.7	$ 68.7
Recognition period of unrecognized compensation expense (in years)	3 years	3 years
Performance Shares
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Vesting period (in years)	3 years
2020 Stock Incentive Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Securities available for future issuance (in shares)	11.3
2020 Stock Incentive Plan \| Employee Stock Option
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expiration term of unexercised options (in years)	7 years

Property and Equipment

12 Months Ended

Sep. 30, 2025

Property, Plant and Equipment [Abstract]

Property and Equipment

Property and equipment, at cost, consists of the following:


	Fiscal Year Ended				Useful Lives (years)
	September 30, 2025		September 30, 2024

	(in millions)
Building and land	$	10.5	$	10.1	10	-	45
Leasehold improvements	275.0		299.3		1	-	20
Computer systems and equipment	770.4		659.6		3	-	12
Furniture and fixtures	85.7		92.2		3	-	10
Total	1,141.6		1,061.2
Accumulated depreciation and amortization	(725.4)		(706.8)
Property and equipment, net	$	416.2	$	354.4

Depreciation expense for the fiscal years ended September 30, 2025, 2024 and 2023 was $166.3 million, $152.3 million, and $152.3 million, respectively. Depreciation is calculated using primarily the straight-line method over the estimated useful lives of the assets, or in the case of leasehold improvements and capitalized leases, the lesser of the remaining term of the lease or its estimated useful life.

Leases - Schedule of Total Remaining Lease Payments Under Operating and Finance Leases (Details) $ in Millions	Sep. 30, 2025 USD ($)
Operating Leases
2026	$ 163.6
2027	135.7
2028	118.1
2029	97.9
2030	75.4
Thereafter	173.3
Total lease payments	764.0
Less: Amounts representing interest	(115.6)
Total lease liabilities	648.4
Finance Leases
2026	35.0
2027	26.1
2028	16.0
2029	4.6
2030	0.0
Thereafter	0.0
Total lease payments	81.7
Less: Amounts representing interest	(5.5)
Total lease liabilities	$ 76.2

Income Taxes - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
Income Taxes - Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Income Tax Contingency [Line Items]
Income (loss) from domestic operations	$ 392.7	$ 233.0	$ (129.2)
Income from foreign operations	522.9	485.2	342.6
Tax benefit related to deferred tax assets resulting from legal entity restructuring	20.1
Increase in tax benefit		38.4
Increase in tax expense related to uncertain tax position		23.0
Increase (decrease) in valuation allowance	(3.8)
Valuation allowance	157.1	160.9
Tax expense (benefit) related to uncertain tax positions	46.7	18.6	9.4
Net operating loss carryforwards	700.7	744.6
Gross deferred tax assets	609.4	678.9
Gross tax asset exclusive of tax liabilities realizable	452.3
Gross book-tax differences from non-U.S. subsidiaries	1,100.0
Liability for unrecognized tax benefits, including potential interest and penalties, net of related tax benefit	144.1	97.9
Unrecognized tax benefits	129.6	81.3	62.1
Unrecognized tax benefits that would be included in the effective tax rate if recognized	125.4
Accrued interest, excluding any related income tax benefits	23.8	27.7
Accrued penalties, excluding any related income tax benefits	3.2	3.5
Capital Loss Carryforward
Income Tax Contingency [Line Items]
Tax credit carryforward	51.7	181.2
Research Tax Credit Carryforward
Income Tax Contingency [Line Items]
Tax credit carryforward, valuation allowance	47.0
Research Tax Credit Carryforward \| State
Income Tax Contingency [Line Items]
Tax credit carryforward	30.5
Research Tax Credit Carryforward \| Foreign
Income Tax Contingency [Line Items]
Tax credit carryforward	0.2
Other Credits
Income Tax Contingency [Line Items]
Tax credit carryforward	3.7
ACAP Investments
Income Tax Contingency [Line Items]
Increase (decrease) in valuation allowance		(21.0)
Reduction in deferred tax assets		20.2
Valuation allowance		9.3
AECOM Capital Impairment Charge
Income Tax Contingency [Line Items]
Valuation allowance			$ 21.0
Capital Losses
Income Tax Contingency [Line Items]
Increase (decrease) in valuation allowance	(5.6)
Foreign Net Operating Losses And Currency Translation Adjustments
Income Tax Contingency [Line Items]
Increase (decrease) in valuation allowance	$ 1.9
CANADA \| Operating Losses and Other Deferred Tax Assets
Income Tax Contingency [Line Items]
Increase (decrease) in valuation allowance		(11.7)
HONG KONG
Income Tax Contingency [Line Items]
Tax expense (benefit) related to uncertain tax positions		$ (6.9)

Leases (Tables)

12 Months Ended

Sep. 30, 2025

Leases [Abstract]

Schedule of Components of Lease Expenses and Additional Cash Flow Information Related to Leases

The components of lease expenses are as follows:


	Fiscal Year Ended
	September 30, 2025		September 30, 2024		September 30, 2023

	(in millions)
Operating lease cost	$	147.4	$	149.1	$	164.0
Finance lease cost:
Amortization of right-of-use assets	33.9		28.4		23.1
Interest on lease liabilities	3.7		2.9		2.6
Variable lease cost	32.0		34.6		34.1
Total lease cost	$	217.0	$	215.0	$	223.8

Additional cash flow information related to leases is as follows:


	Fiscal Year Ended
	September 30, 2025		September 30, 2024		September 30, 2023

	(in millions)
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$	172.6	$	184.9	$	188.3
Operating cash flows from finance leases	3.7		3.0		2.5
Financing cash flows from finance leases	32.4		28.9		23.7
Right-of-use assets obtained in exchange for new operating leases	130.9		90.1		96.6
Right-of-use assets obtained in exchange for new finance leases	47.2		26.6		37.5

Schedule of Additional Balance Sheet Information Related to Leases

Additional balance sheet information related to leases is as follows:


(in millions except as noted)	Balance Sheet Classification	September 30, 2025		September 30, 2024
Assets:
Operating lease assets	Operating lease right-of-use assets	$	463.5	$	432.2
Finance lease assets	Property and equipment – net	74.4		62.1
Total lease assets		$	537.9	$	494.3

Liabilities:
Current:
Operating lease liabilities	Accrued expenses and other current liabilities	$	132.4	$	135.1
Finance lease liabilities	Current portion of long-term debt	31.9		25.5
Total current lease liabilities		164.3		160.6
Non-current:
Operating lease liabilities	Operating lease liabilities, noncurrent	516.0		510.6
Finance lease liabilities	Long-term debt	44.3		35.7
Total non-current lease liabilities		$	560.3	$	546.3


	As of
	September 30, 2025		September 30, 2024		September 30, 2023
Weighted average remaining lease term (in years):
Operating leases	6.1		6.2		6.4
Finance leases	2.7		2.6		2.9
Weighted average discount rates:
Operating leases	5.2	%	5.1	%	4.3	%
Finance leases	4.8	%	4.4	%	4.1	%

Schedule of Operating Lease, Liability, to be Paid, Maturity

Total remaining lease payments under both the Company’s operating and finance leases are as follows:


	Operating Leases		Finance Leases

Fiscal Year	(in millions)
2026	$	163.6	$	35.0
2027	135.7		26.1
2028	118.1		16.0
2029	97.9		4.6
2030	75.4		—
Thereafter	173.3		—
Total lease payments	$	764.0	$	81.7
Less: Amounts representing interest	$	(115.6)	$	(5.5)
Total lease liabilities	$	648.4	$	76.2

Schedule of Finance Lease, Liability, to be Paid, Maturity

Total remaining lease payments under both the Company’s operating and finance leases are as follows:


	Operating Leases		Finance Leases

Fiscal Year	(in millions)
2026	$	163.6	$	35.0
2027	135.7		26.1
2028	118.1		16.0
2029	97.9		4.6
2030	75.4		—
Thereafter	173.3		—
Total lease payments	$	764.0	$	81.7
Less: Amounts representing interest	$	(115.6)	$	(5.5)
Total lease liabilities	$	648.4	$	76.2

Property and Equipment - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 166.3	$ 152.3	$ 152.3

Pension Benefit Obligations - Schedule of Reconciliations of Funded Status (Details) - USD ($) $ in Millions	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
U.S.
Reconciliation of funded status:
Funded status at end of year	$ (72.0)	$ (77.9)	$ (82.4)
Net amount recognized at end of year	(72.0)	(77.9)	(82.4)
Int’l
Reconciliation of funded status:
Funded status at end of year	(17.4)	(56.1)	(82.9)
Net amount recognized at end of year	$ (17.4)	$ (56.1)	$ (82.9)

Debt - Effective Interest Rate (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Debt Disclosure [Abstract]
Effective interest rate (as percent)	5.10%	5.60%	5.30%
Amortization of deferred debt issuance costs	$ 7.4	$ 7.6	$ 4.9

Pension Benefit Obligations - Schedule of Components of Net Periodic Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
U.S.
Defined Benefit Plan Disclosure [Line Items]
Service costs	$ 0.0	$ 0.0	$ 0.0
Interest cost on projected benefit obligation	$ 7.9	$ 9.7	$ 9.8
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Interest Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income	Other income	Other income
Expected return on plan assets	$ (4.8)	$ (5.5)	$ (5.8)
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Expected Return (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income	Other income	Other income
Amortization of prior service costs	$ 0.0	$ 0.0	$ 0.0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Amortization of Prior Service Cost (Credit), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income	Other income	Other income
Amortization of net loss (gain)	$ 3.7	$ 3.1	$ 3.5
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Amortization of Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income	Other income	Other income
Settlement loss (gain) recognized	$ 0.1	$ 0.0	$ (0.1)
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Settlement Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income	Other income	Other income
Net periodic benefit cost (credit)	$ 6.9	$ 7.3	$ 7.4
Int’l
Defined Benefit Plan Disclosure [Line Items]
Service costs	0.2	0.2	0.3
Interest cost on projected benefit obligation	$ 40.1	$ 43.7	$ 47.7
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Interest Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income	Other income	Other income
Expected return on plan assets	$ (52.2)	$ (57.4)	$ (60.8)
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Expected Return (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income	Other income	Other income
Amortization of prior service costs	$ 0.1	$ 0.1	$ 0.1
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Amortization of Prior Service Cost (Credit), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income	Other income	Other income
Amortization of net loss (gain)	$ (1.3)	$ (2.3)	$ (0.6)
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Amortization of Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income	Other income	Other income
Settlement loss (gain) recognized	$ 0.0	$ 0.1	$ 0.2
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Settlement Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income	Other income	Other income
Net periodic benefit cost (credit)	$ (13.1)	$ (15.6)	$ (13.1)

Significant Accounting Policies	12 Months Ended
Significant Accounting Policies	Sep. 30, 2025
Accounting Policies [Abstract]
Significant Accounting Policies	Significant Accounting Policies Organization— AECOM and its consolidated subsidiaries provide planning, consulting, advisory, architectural and engineering design services, construction management and program management to public and private clients worldwide in major end markets such as transportation, facilities, environmental, energy, water and government. Fiscal Year—The Company reports its annual results of operations based on 52-or 53- week periods ending on the Friday nearest September 30. Certain prior period amounts in the consolidated financial statements and accompanying notes have been reclassified to conform with the current period’s presentation. Use of Estimates—The preparation of financial statements in conformity with accounting principles generally accepted in the United States (GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. The more significant estimates affecting amounts reported in the consolidated financial statements relate to revenues under long-term contracts and self-insurance accruals. Actual results could differ from those estimates. Principles of Consolidation and Presentation—The consolidated financial statements include the accounts of all majority-owned subsidiaries and joint ventures in which the Company is the primary beneficiary. All inter-company accounts have been eliminated in consolidation. Also see Note 6 regarding joint ventures and variable interest entities. Government Contract Matters—The Company’s federal government and certain state and local agency contracts are subject to, among other regulations, regulations issued under the Federal Acquisition Regulations (FAR). These regulations can limit the recovery of certain specified indirect costs on contracts and subjects the Company to ongoing multiple audits by government agencies such as the Defense Contract Audit Agency (DCAA). In addition, most of the Company’s federal and state and local contracts are subject to termination at the discretion of the client. Audits by the DCAA and other agencies consist of reviews of the Company’s overhead rates, operating systems and cost proposals to ensure that the Company accounted for such costs in accordance with the Cost Accounting Standards of the FAR (CAS). If the DCAA determines the Company has not accounted for such costs consistent with CAS, the DCAA may disallow these costs. There can be no assurance that audits by the DCAA or other governmental agencies will not result in material cost disallowances in the future. Cash and Cash Equivalents—The Company’s cash equivalents include highly liquid investments which have an initial maturity of three months or less. Allowance for Doubtful Accounts—The Company records its accounts receivable net of an allowance for doubtful accounts. This allowance for doubtful accounts is estimated based on management’s evaluation of the contracts involved and the financial condition of its clients. The factors the Company considers in its contract evaluations include, but are not limited to: •Client type—federal or state and local government or commercial client; •Historical contract performance; •Historical collection and delinquency trends; •Client credit worthiness; and •General economic conditions. Derivative Financial Instruments—The Company accounts for its derivative instruments as either assets or liabilities and carries them at fair value. For derivative instruments that hedge the exposure to variability in expected future cash flows that are designated as cash flow hedges, the effective portion of the gain or loss on the derivative instrument is reported as a component of accumulated other comprehensive income in stockholders’ equity and reclassified into income in the same period or periods during which the hedged transaction affects earnings. The ineffective portion of the gain or loss on the derivative instrument, if any, is recognized in current income. To receive hedge accounting treatment, cash flow hedges must be highly effective in offsetting changes to expected future cash flows on hedged transactions. The net gain or loss on the effective portion of a derivative instrument that is designated as an economic hedge of the foreign currency translation exposure generated by the re-measurement of certain assets and liabilities denominated in a non-functional currency in a foreign operation is reported in the same manner as a foreign currency translation adjustment. Accordingly, any gains or losses related to these derivative instruments are recognized in current income. Derivatives that do not qualify as hedges are adjusted to fair value through current income. Fair Value of Financial Instruments—The Company determines the fair values of its financial instruments, including short-term investments, debt instruments and derivative instruments, and pension and post-retirement plan assets based on inputs or assumptions that market participants would use in pricing an asset or a liability. The Company categorizes its instruments using a valuation hierarchy for disclosure of the inputs used to measure fair value. This hierarchy prioritizes the inputs into three broad levels as follows: Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities; Level 2 inputs are quoted prices for similar assets and liabilities in active markets or inputs that are observable for the asset or liability, either directly or indirectly through market corroboration, for substantially the full term of the financial instrument; Level 3 inputs are unobservable inputs based on the Company’s assumptions used to measure assets and liabilities at fair value. The classification of a financial asset or liability within the hierarchy is determined based on the lowest level input that is significant to the fair value measurement. The carrying amounts of cash and cash equivalents, accounts receivable and accounts payable approximate fair value because of the short maturities of these instruments. The carrying amount of the revolving credit facility approximates fair value because the interest rates are based upon variable reference rates. The Company’s fair value measurement methods may produce a fair value calculation that may not be indicative of net realizable value or reflective of future fair values. Although the Company believes its valuation methods are appropriate and consistent with those used by other market participants, the use of different methodologies or assumptions to determine fair value could result in a different fair value measurement at the reporting date. Property and Equipment—Property and equipment are recorded at cost and are depreciated over their estimated useful lives using the straight-line method. Expenditures for maintenance and repairs are expensed as incurred. Typically, estimated useful lives range from ten to forty-five years for buildings, three to ten years for furniture and fixtures and three to twelve years for computer systems and equipment. Leasehold improvements are amortized on a straight-line basis over the shorter of their estimated useful lives or the remaining terms of the underlying lease agreement. Long-Lived Assets—Long-lived assets to be held and used are reviewed for impairment whenever events or circumstances indicate that the assets may not be recoverable. The carrying amount of an asset to be held and used is not recoverable if it exceeds the sum of the undiscounted cash flows expected from the use and eventual disposition of the asset. For assets to be held and used, impairment losses are recognized based upon the excess of the asset’s carrying amount over the fair value of the asset. For long-lived assets to be disposed, impairment losses are recognized at the lower of the carrying amount or fair value less cost to sell. Goodwill and Acquired Intangible Assets—Goodwill represents the excess of amounts paid over the fair value of net assets acquired from an acquisition. In order to determine the amount of goodwill resulting from an acquisition, the Company performs an assessment to determine the value of the acquired company’s tangible and identifiable intangible assets and liabilities. In its assessment, the Company determines whether identifiable intangible assets exist, which typically include backlog, customer relationships and intellectual property. Intangible assets are amortized over the period in which the contractual or economic benefits of the intangible assets are expected to be realized. The Company tests goodwill for impairment annually for each reporting unit in the fourth quarter of the fiscal year and between annual tests, if events occur or circumstances change which suggest that goodwill should be evaluated. Such events or circumstances include significant changes in legal factors and business climate, recent losses at a reporting unit, and industry trends, among other factors. A reporting unit is defined as an operating segment or one level below an operating segment. The Company’s impairment tests are performed at the operating segment level as they represent the Company’s reporting units. Goodwill is evaluated for impairment either by assessing qualitative factors or by performing a quantitative assessment. Qualitative factors, such as overall financial performance, industry or market considerations, or other relevant events, are assessed to determine if it is more likely than not that the fair value of the reporting units is less than their carrying amounts. During a quantitative impairment test, the Company estimates the fair value of the reporting unit using income and market approaches, and compares that amount to the carrying value of that reporting unit. In the event the fair value of the reporting unit is determined to be less than the carrying value, goodwill is impaired, and an impairment loss is recognized equal to the excess, limited to the total amount of goodwill allocated to the reporting unit. The impairment evaluation process includes, among other things, making assumptions about variable such as revenue growth rates, profitability, discount rates, and industry market multiples, which are subject to a high degree of judgment. See also Note 3. Pension Plans—The Company has certain defined benefit pension plans. The Company calculates the market-related value of assets, which is used to determine the return-on-assets component of annual pension expense and the cumulative net unrecognized gain or loss subject to amortization. This calculation reflects the Company’s anticipated long-term rate of return and amortization of the difference between the actual return (including capital, dividends, and interest) and the expected return over a five-year period. Cumulative net unrecognized gains or losses that exceed 10% of the greater of the projected benefit obligation or the fair market related value of plan assets are subject to amortization. Insurance Reserves—The Company maintains insurance for certain insurable business risks. Insurance coverage contains various retention and deductible amounts for which the Company accrues a liability based upon reported claims and an actuarially determined estimated liability for certain claims incurred but not reported. It is generally the Company’s policy not to accrue for any potential legal expense to be incurred in defending the Company’s position. The Company believes that its accruals for estimated liabilities associated with professional and other liabilities are sufficient and any excess liability beyond the accrual is not expected to have a material adverse effect on the Company’s results of operations or financial position. Foreign Currency Translation—The Company’s functional currency is generally the U.S. dollar, except for foreign operations where the functional currency is generally the local currency. Results of operations for foreign entities are translated to U.S. dollars using the average exchange rates during the period. Assets and liabilities for foreign entities are translated using the exchange rates in effect as of the date of the balance sheet. Resulting translation adjustments are recorded as a foreign currency translation adjustment into other accumulated comprehensive income/(loss) in stockholders’ equity. The Company uses foreign currency forward contracts from time to time to mitigate foreign currency risk. The Company limits exposure to foreign currency fluctuations in most of its contracts through provisions that require client payments in currencies corresponding to the currency in which costs are incurred. As a result of this natural hedge, the Company generally does not need to hedge foreign currency cash flows for contract work performed. Noncontrolling Interests—Noncontrolling interests represent the equity investments of the minority owners in the Company’s joint ventures and other subsidiary entities that the Company consolidates in its financial statements. Income Taxes—The Company files a consolidated U.S. federal corporate income tax return and combined / consolidated state tax returns and separate company state tax returns. The Company accounts for certain income and expense items differently for financial reporting and income tax purposes. Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax basis of assets and liabilities, applying enacted statutory tax rates in effect for the year in which the differences are expected to reverse. In determining the need for a valuation allowance, management reviews both positive and negative evidence, including the nature, frequency, and severity of cumulative financial reporting losses in recent years, the future reversal of existing temporary differences, predictability of future taxable income exclusive of reversing temporary differences of the character necessary to realize the asset, relevant carryforward periods, taxable income in carry-back years if carry-back is permitted under tax law, and prudent and feasible tax planning strategies that would be implemented, if necessary, to protect against the loss of the deferred tax asset that would otherwise expire. Based upon management’s assessment of all available evidence, the Company has concluded that it is more likely than not that the deferred tax assets, net of valuation allowance, will be realized. On December 22, 2017, the United States enacted the Tax Cuts and Jobs Act, which significantly changed U.S. tax law and included a provision to tax global intangible low-taxed income (GILTI) of foreign subsidiaries. The Company recognizes taxes due under the GILTI provision as a current period expense. On July 4, 2025, the U.S. government enacted the One Big Beautiful Bill Act which permanently extends many provisions of the Tax Cuts and Jobs Act of 2017 and introduces new tax provisions relevant for multinational businesses. Most of the new provisions take effect starting in fiscal 2026. Based on its assessment, the Company does not expect the legislation to have a material impact on its consolidated financial statements.

Discontinued Operations, Goodwill and Intangible Assets - Narrative (Details) $ in Thousands			3 Months Ended			12 Months Ended
	Jan. 31, 2020	Dec. 06, 2019 USD ($)	Jun. 30, 2025 USD ($)	Jun. 30, 2024 USD ($)	Mar. 31, 2024 USD ($)	Sep. 30, 2025 USD ($) acquisition	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Dec. 31, 2014 USD ($)	Feb. 28, 2011 USD ($)
Discontinued Operations, Goodwill and Intangible Assets
Losses related to contingent consideration receivable recognized						$ 0	$ 90,412	$ 43,222
Amortization expense of acquired intangible assets						$ 1,500	18,800
2025 Acquisitions
Discontinued Operations, Goodwill and Intangible Assets
Number of business acquisitions \| acquisition						2
Total consideration						$ 375,900
Stock consideration						146,400
Task Order, Deactivation Demolition And Removal Service
Discontinued Operations, Goodwill and Intangible Assets
Percentage of claim recoveries due to purchaser	10.00%
Percentage of claim recoveries due to seller	90.00%
Refinery Turnaround Project
Discontinued Operations, Goodwill and Intangible Assets
Loss from reduction in expected future net cash proceeds			$ 53,000
Department of Energy \| Task Order, Deactivation Demolition And Removal Service
Discontinued Operations, Goodwill and Intangible Assets
Maximum project cost to pay										$ 106,000
Additional fees on changed work scope		$ 60,400							$ 103,000
Department of Energy \| Task Order, Deactivation Demolition And Removal Service \| Minimum \| Former Affiliate
Discontinued Operations, Goodwill and Intangible Assets
Damages sought		148,500
Department of Energy \| Task Order, Deactivation Demolition And Removal Service \| Maximum \| Former Affiliate
Discontinued Operations, Goodwill and Intangible Assets
Damages sought		$ 329,400
Former Affiliate and DOE \| Task Order, Deactivation Demolition And Removal Service
Discontinued Operations, Goodwill and Intangible Assets
Maximum project cost to pay										146,000
Minimum project cost to pay										106,000
Former Affiliate \| Task Order, Deactivation Demolition And Removal Service
Discontinued Operations, Goodwill and Intangible Assets
Minimum project cost to pay										$ 146,000
Held for Sale
Discontinued Operations, Goodwill and Intangible Assets
Losses related to contingent consideration receivable recognized						83,800	97,100	$ 50,600
Non-cash gain in discontinued operations							$ 12,700
Held for Sale \| Revolving Credit Facility
Discontinued Operations, Goodwill and Intangible Assets
Investment commitment to fund				$ 30,000
Fund outflow in other investing activities and outstanding						$ 15,400
Held for Sale \| Civil Infrastructure Construction Business
Discontinued Operations, Goodwill and Intangible Assets
Losses related to contingent consideration receivable recognized					$ 103,100
Gain based on fair value of equity received				$ 12,700

Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2025	Sep. 30, 2024
CURRENT ASSETS:
Cash and cash equivalents	$ 1,378,582	$ 1,316,945
Cash in consolidated joint ventures	207,157	263,932
Total cash and cash equivalents	1,585,739	1,580,877
Accounts receivable—net	2,497,147	2,793,307
Contract assets	1,785,179	1,806,458
Prepaid expenses and other current assets	716,070	638,393
Current assets held for sale	0	77,224
Income taxes receivable	146,092	159,500
TOTAL CURRENT ASSETS	6,730,227	7,055,759
PROPERTY AND EQUIPMENT—NET	416,164	354,377
DEFERRED TAX ASSETS—NET	295,249	326,685
INVESTMENTS IN UNCONSOLIDATED JOINT VENTURES	138,056	138,067
GOODWILL	3,700,619	3,480,155
INTANGIBLE ASSETS—NET	183,284	6,932
OTHER NON-CURRENT ASSETS	254,218	267,528
OPERATING LEASE RIGHT-OF-USE ASSETS	463,479	432,166
NON-CURRENT ASSETS HELD FOR SALE	18,953	0
TOTAL ASSETS	12,200,249	12,061,669
CURRENT LIABILITIES:
Short-term debt	4,069	3,080
Accounts payable	2,260,609	2,560,122
Accrued expenses and other current liabilities	2,490,480	2,385,731
Income taxes payable	23,536	27,418
Contract liabilities	1,087,905	1,298,327
Current liabilities held for sale	0	35,559
Current portion of long-term debt	62,217	63,844
TOTAL CURRENT LIABILITIES	5,928,816	6,374,081
OTHER LONG-TERM LIABILITIES	210,870	156,406
OPERATING LEASE LIABILITIES, NON-CURRENT	515,998	510,573
DEFERRED TAX LIABILITY-NET	67,968	27,509
PENSION BENEFIT OBLIGATIONS	133,193	172,360
LONG-TERM DEBT	2,647,220	2,450,330
TOTAL LIABILITIES	9,504,065	9,691,259
COMMITMENTS AND CONTINGENCIES (Note 18)
AECOM STOCKHOLDERS’ EQUITY:
Common stock—authorized, 300,000,000 shares of $0.01 par value as of September 30, 2024 and 2023; issued and outstanding 132,552,407 and 136,210,883 shares as of September 30, 2024 and 2023, respectively	1,318	1,326
Additional paid-in capital	4,609,126	4,347,197
Accumulated other comprehensive loss	(893,027)	(882,671)
Accumulated deficits	(1,224,833)	(1,281,647)
TOTAL AECOM STOCKHOLDERS’ EQUITY	2,492,584	2,184,205
Noncontrolling interests	203,600	186,205
TOTAL STOCKHOLDERS’ EQUITY	2,696,184	2,370,410
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$ 12,200,249	$ 12,061,669

Leases

12 Months Ended

Sep. 30, 2025

Leases [Abstract]

Leases

The Company and its subsidiaries are lessees in non-cancelable leasing agreements for office buildings and equipment. Substantially all of the Company’s office building leases are operating leases, and its equipment leases are both operating and finance leases. The Company groups lease and non-lease components for its equipment leases into a single lease component but separates lease and non-lease components for its office building leases.

The Company recognizes a right-of-use asset and lease liability for its operating leases at the commencement date equal to the present value of the contractual minimum lease payments over the lease term. The present value is calculated using the rate implicit in the lease, if known, or the Company’s incremental secured borrowing rate. The discount rate used for operating leases is primarily determined based on an analysis of the Company’s incremental secured borrowing rate, while the discount rate used for finance leases is primarily determined by the rate specified in the lease.

The related lease payments are expensed on a straight-line basis over the lease term, including, as applicable, any free-rent period during which the Company has the right to use the asset. For leases with renewal options where the renewal is reasonably assured, the lease term, including the renewal period, is used to determine the appropriate lease classification and to compute periodic rental expense. Leases with initial terms shorter than 12 months are not recognized on the balance sheet, and lease expense is recognized on a straight-line basis.

During the fourth quarter of fiscal 2023, the Company approved a restructuring plan primarily to optimize its office real estate portfolio with its freedom to grow strategy, which initiated a review of the carrying value of right-of-use assets and leasehold improvements. In connection with the review, the Company identified leased assets that were no longer recoverable. The Company recorded an impairment charge of $86.2 million to reduce its right-of-use assets and leasehold improvements to their fair values and recorded the expense in restructuring costs on the Consolidated Statement of Operations. Fair value was determined primarily using Level 3 inputs, such as discounted cash flows.

The components of lease expenses are as follows:


	Fiscal Year Ended
	September 30, 2025		September 30, 2024		September 30, 2023

	(in millions)
Operating lease cost	$	147.4	$	149.1	$	164.0
Finance lease cost:
Amortization of right-of-use assets	33.9		28.4		23.1
Interest on lease liabilities	3.7		2.9		2.6
Variable lease cost	32.0		34.6		34.1
Total lease cost	$	217.0	$	215.0	$	223.8

Additional balance sheet information related to leases is as follows:


(in millions except as noted)	Balance Sheet Classification	September 30, 2025		September 30, 2024
Assets:
Operating lease assets	Operating lease right-of-use assets	$	463.5	$	432.2
Finance lease assets	Property and equipment – net	74.4		62.1
Total lease assets		$	537.9	$	494.3

Liabilities:
Current:
Operating lease liabilities	Accrued expenses and other current liabilities	$	132.4	$	135.1
Finance lease liabilities	Current portion of long-term debt	31.9		25.5
Total current lease liabilities		164.3		160.6
Non-current:
Operating lease liabilities	Operating lease liabilities, noncurrent	516.0		510.6
Finance lease liabilities	Long-term debt	44.3		35.7
Total non-current lease liabilities		$	560.3	$	546.3


	As of
	September 30, 2025		September 30, 2024		September 30, 2023
Weighted average remaining lease term (in years):
Operating leases	6.1		6.2		6.4
Finance leases	2.7		2.6		2.9
Weighted average discount rates:
Operating leases	5.2	%	5.1	%	4.3	%
Finance leases	4.8	%	4.4	%	4.1	%

Additional cash flow information related to leases is as follows:


	Fiscal Year Ended
	September 30, 2025		September 30, 2024		September 30, 2023

	(in millions)
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$	172.6	$	184.9	$	188.3
Operating cash flows from finance leases	3.7		3.0		2.5
Financing cash flows from finance leases	32.4		28.9		23.7
Right-of-use assets obtained in exchange for new operating leases	130.9		90.1		96.6
Right-of-use assets obtained in exchange for new finance leases	47.2		26.6		37.5

Total remaining lease payments under both the Company’s operating and finance leases are as follows:


	Operating Leases		Finance Leases

Fiscal Year	(in millions)
2026	$	163.6	$	35.0
2027	135.7		26.1
2028	118.1		16.0
2029	97.9		4.6
2030	75.4		—
Thereafter	173.3		—
Total lease payments	$	764.0	$	81.7
Less: Amounts representing interest	$	(115.6)	$	(5.5)
Total lease liabilities	$	648.4	$	76.2

Leases

The components of lease expenses are as follows:


	Fiscal Year Ended
	September 30, 2025		September 30, 2024		September 30, 2023

	(in millions)
Operating lease cost	$	147.4	$	149.1	$	164.0
Finance lease cost:
Amortization of right-of-use assets	33.9		28.4		23.1
Interest on lease liabilities	3.7		2.9		2.6
Variable lease cost	32.0		34.6		34.1
Total lease cost	$	217.0	$	215.0	$	223.8

Additional balance sheet information related to leases is as follows:


(in millions except as noted)	Balance Sheet Classification	September 30, 2025		September 30, 2024
Assets:
Operating lease assets	Operating lease right-of-use assets	$	463.5	$	432.2
Finance lease assets	Property and equipment – net	74.4		62.1
Total lease assets		$	537.9	$	494.3

Liabilities:
Current:
Operating lease liabilities	Accrued expenses and other current liabilities	$	132.4	$	135.1
Finance lease liabilities	Current portion of long-term debt	31.9		25.5
Total current lease liabilities		164.3		160.6
Non-current:
Operating lease liabilities	Operating lease liabilities, noncurrent	516.0		510.6
Finance lease liabilities	Long-term debt	44.3		35.7
Total non-current lease liabilities		$	560.3	$	546.3


	As of
	September 30, 2025		September 30, 2024		September 30, 2023
Weighted average remaining lease term (in years):
Operating leases	6.1		6.2		6.4
Finance leases	2.7		2.6		2.9
Weighted average discount rates:
Operating leases	5.2	%	5.1	%	4.3	%
Finance leases	4.8	%	4.4	%	4.1	%

Additional cash flow information related to leases is as follows:


	Fiscal Year Ended
	September 30, 2025		September 30, 2024		September 30, 2023

	(in millions)
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$	172.6	$	184.9	$	188.3
Operating cash flows from finance leases	3.7		3.0		2.5
Financing cash flows from finance leases	32.4		28.9		23.7
Right-of-use assets obtained in exchange for new operating leases	130.9		90.1		96.6
Right-of-use assets obtained in exchange for new finance leases	47.2		26.6		37.5

Total remaining lease payments under both the Company’s operating and finance leases are as follows:


	Operating Leases		Finance Leases

Fiscal Year	(in millions)
2026	$	163.6	$	35.0
2027	135.7		26.1
2028	118.1		16.0
2029	97.9		4.6
2030	75.4		—
Thereafter	173.3		—
Total lease payments	$	764.0	$	81.7
Less: Amounts representing interest	$	(115.6)	$	(5.5)
Total lease liabilities	$	648.4	$	76.2

Leases - Narrative (Details) $ in Millions	3 Months Ended
Leases - Narrative (Details) $ in Millions	Sep. 30, 2023 USD ($)
Leases [Abstract]
Impairment of leasehold and right of use assets	$ 86.2

Major Clients	12 Months Ended
Major Clients	Sep. 30, 2025
Major Clients [Abstract]
Major Clients	Concentration of Credit Risk Financial instruments which potentially subject the Company to concentrations of credit risk consist principally of cash investments and trade receivables. The Company’s cash balances and short-term investments are maintained in accounts held by major banks and financial institutions located primarily in the U.S., Canada, Europe, Australia, Middle East and Hong Kong. If the Company extends significant credit to clients in a specific geographic area or industry, the Company may experience disproportionately high levels of default if those clients are adversely affected by factors particular to their geographic area or industry. Concentrations of credit risk with respect to trade receivables are limited due to the large number of customers comprising the Company’s customer base, including, in large part, governments, government agencies and quasi-government organizations, and their dispersion across many different industries and geographies. See Note 4 regarding the Company’s foreign revenues. In order to mitigate credit risk, the Company continually reviews the credit worthiness of its major private clients. Major Clients No single client accounted for 10% or more of the Company’s revenue in any of the past five fiscal years. Approximately 7%, 7%, and 5% of the Company’s revenue was derived through direct contracts with agencies of the U.S. federal government in the years ended September 30, 2025, 2024 and 2023, respectively.

- Definition

+ References

+ Details

Property and Equipment (Tables)

12 Months Ended

Sep. 30, 2025

Property, Plant and Equipment [Abstract]

Schedule of Property and Equipment, at Cost

Property and equipment, at cost, consists of the following:


	Fiscal Year Ended				Useful Lives (years)
	September 30, 2025		September 30, 2024

	(in millions)
Building and land	$	10.5	$	10.1	10	-	45
Leasehold improvements	275.0		299.3		1	-	20
Computer systems and equipment	770.4		659.6		3	-	12
Furniture and fixtures	85.7		92.2		3	-	10
Total	1,141.6		1,061.2
Accumulated depreciation and amortization	(725.4)		(706.8)
Property and equipment, net	$	416.2	$	354.4

Derivative Financial Instruments and Fair Value Measurements - Schedule of Financial Assets and Liabilities Recorded at Fair Value on a Recurring Basis (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Millions	Sep. 30, 2025	Sep. 30, 2024
Derivative [Line Items]
Credit facility investment	$ 17.4	$ 21.9
Contingent Consideration	(7.5)
Equity investment	21.9	19.4
Total net assets at fair value	46.2	62.5
Other current assets
Derivative [Line Items]
Derivative asset	$ 9.0	$ 9.2
Derivative Asset, Current, Statement of Financial Position [Extensible Enumeration]	Prepaid Expense and Other Assets, Current	Prepaid Expense and Other Assets, Current
Other non-current assets
Derivative [Line Items]
Derivative asset	$ 10.0	$ 16.5
Derivative Asset, Current, Statement of Financial Position [Extensible Enumeration]	OTHER NON-CURRENT ASSETS	OTHER NON-CURRENT ASSETS
Other current liabilities
Derivative [Line Items]
Derivative liability	$ 1.8	$ 0.9
Derivative Liability, Current, Statement of Financial Position [Extensible Enumeration]	Accrued expenses and other current liabilities	Accrued expenses and other current liabilities
Other non-current liabilities
Derivative [Line Items]
Derivative liability	$ 2.8	$ 3.6
Derivative Liability, Current, Statement of Financial Position [Extensible Enumeration]	OTHER LONG-TERM LIABILITIES	OTHER LONG-TERM LIABILITIES
Quoted Prices in Active Markets for Identical Assets (Level 1)
Derivative [Line Items]
Credit facility investment	$ 0.0	$ 0.0
Contingent Consideration	0.0
Equity investment	21.9	19.4
Total net assets at fair value	21.9	19.4
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Other current assets
Derivative [Line Items]
Derivative asset	$ 0.0	$ 0.0
Derivative Asset, Current, Statement of Financial Position [Extensible Enumeration]	Prepaid Expense and Other Assets, Current	Prepaid Expense and Other Assets, Current
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Other non-current assets
Derivative [Line Items]
Derivative asset	$ 0.0	$ 0.0
Derivative Asset, Current, Statement of Financial Position [Extensible Enumeration]	OTHER NON-CURRENT ASSETS	OTHER NON-CURRENT ASSETS
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Other current liabilities
Derivative [Line Items]
Derivative liability	$ 0.0	$ 0.0
Derivative Liability, Current, Statement of Financial Position [Extensible Enumeration]	Accrued expenses and other current liabilities	Accrued expenses and other current liabilities
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Other non-current liabilities
Derivative [Line Items]
Derivative liability	$ 0.0	$ 0.0
Derivative Liability, Current, Statement of Financial Position [Extensible Enumeration]	OTHER LONG-TERM LIABILITIES	OTHER LONG-TERM LIABILITIES
Significant Observable Inputs (Level 2)
Derivative [Line Items]
Credit facility investment	$ 0.0	$ 0.0
Contingent Consideration	(7.5)
Equity investment	0.0	0.0
Total net assets at fair value	6.9	21.2
Significant Observable Inputs (Level 2) \| Other current assets
Derivative [Line Items]
Derivative asset	$ 9.0	$ 9.2
Derivative Asset, Current, Statement of Financial Position [Extensible Enumeration]	Prepaid Expense and Other Assets, Current	Prepaid Expense and Other Assets, Current
Significant Observable Inputs (Level 2) \| Other non-current assets
Derivative [Line Items]
Derivative asset	$ 10.0	$ 16.5
Derivative Asset, Current, Statement of Financial Position [Extensible Enumeration]	OTHER NON-CURRENT ASSETS	OTHER NON-CURRENT ASSETS
Significant Observable Inputs (Level 2) \| Other current liabilities
Derivative [Line Items]
Derivative liability	$ 1.8	$ 0.9
Derivative Liability, Current, Statement of Financial Position [Extensible Enumeration]	Accrued expenses and other current liabilities	Accrued expenses and other current liabilities
Significant Observable Inputs (Level 2) \| Other non-current liabilities
Derivative [Line Items]
Derivative liability	$ 2.8	$ 3.6
Derivative Liability, Current, Statement of Financial Position [Extensible Enumeration]	OTHER LONG-TERM LIABILITIES	OTHER LONG-TERM LIABILITIES
Significant Unobservable Inputs (Level 3)
Derivative [Line Items]
Credit facility investment	$ 17.4	$ 21.9
Contingent Consideration	0.0
Equity investment	0.0	0.0
Total net assets at fair value	17.4	21.9
Significant Unobservable Inputs (Level 3) \| Other current assets
Derivative [Line Items]
Derivative asset	$ 0.0	$ 0.0
Derivative Asset, Current, Statement of Financial Position [Extensible Enumeration]	Prepaid Expense and Other Assets, Current	Prepaid Expense and Other Assets, Current
Significant Unobservable Inputs (Level 3) \| Other non-current assets
Derivative [Line Items]
Derivative asset	$ 0.0	$ 0.0
Derivative Asset, Current, Statement of Financial Position [Extensible Enumeration]	OTHER NON-CURRENT ASSETS	OTHER NON-CURRENT ASSETS
Significant Unobservable Inputs (Level 3) \| Other current liabilities
Derivative [Line Items]
Derivative liability	$ 0.0	$ 0.0
Derivative Liability, Current, Statement of Financial Position [Extensible Enumeration]	Accrued expenses and other current liabilities	Accrued expenses and other current liabilities
Significant Unobservable Inputs (Level 3) \| Other non-current liabilities
Derivative [Line Items]
Derivative liability	$ 0.0	$ 0.0
Derivative Liability, Current, Statement of Financial Position [Extensible Enumeration]	OTHER LONG-TERM LIABILITIES	OTHER LONG-TERM LIABILITIES

Pension Benefit Obligations - Schedule of Target Allocation and Pension Plan Asset Allocation (Details)	Sep. 30, 2025	Sep. 30, 2024
U.S.
Defined Benefit Plan Disclosure [Line Items]
Target Allocations (as percent)	100.00%
Percentage of Plan Assets (as percent)	100.00%	100.00%
U.S. \| Equities
Defined Benefit Plan Disclosure [Line Items]
Target Allocations (as percent)	18.00%
Percentage of Plan Assets (as percent)	19.00%	24.00%
U.S. \| Debt
Defined Benefit Plan Disclosure [Line Items]
Target Allocations (as percent)	78.00%
Percentage of Plan Assets (as percent)	74.00%	67.00%
U.S. \| Cash
Defined Benefit Plan Disclosure [Line Items]
Target Allocations (as percent)	0.00%
Percentage of Plan Assets (as percent)	2.00%	4.00%
U.S. \| Diversified and other
Defined Benefit Plan Disclosure [Line Items]
Target Allocations (as percent)	4.00%
Percentage of Plan Assets (as percent)	5.00%	5.00%
Int’l
Defined Benefit Plan Disclosure [Line Items]
Target Allocations (as percent)	100.00%
Percentage of Plan Assets (as percent)	100.00%	100.00%
Int’l \| Equities
Defined Benefit Plan Disclosure [Line Items]
Target Allocations (as percent)	25.00%
Percentage of Plan Assets (as percent)	24.00%	25.00%
Int’l \| Debt
Defined Benefit Plan Disclosure [Line Items]
Target Allocations (as percent)	65.00%
Percentage of Plan Assets (as percent)	64.00%	64.00%
Int’l \| Cash
Defined Benefit Plan Disclosure [Line Items]
Target Allocations (as percent)	3.00%
Percentage of Plan Assets (as percent)	2.00%	2.00%
Int’l \| Diversified and other
Defined Benefit Plan Disclosure [Line Items]
Target Allocations (as percent)	7.00%
Percentage of Plan Assets (as percent)	10.00%	9.00%

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

Share-Based Payments (Tables)

12 Months Ended

Sep. 30, 2025

Share-Based Payment Arrangement [Abstract]

Schedule of Restricted Stock Units and PEP Units Activity

Restricted stock unit and PEP unit activity for the year ended September 30 was as follows:


	Restricted Stock Units	Weighted Average Grant-Date Fair Value		PEP Units	Weighted Average Grant-Date Fair Value

	(in millions)			(in millions)
Outstanding at September 30, 2022	1.0	$	53.05	0.7	$	60.60
Granted	0.3	$	83.64	0.2	$	94.64
PEP units earned (unearned)	—	$	—	0.2	$	43.19
Vested	(0.4)	$	44.35	(0.4)	$	43.19
Cancelled	(0.1)	$	62.09	—	$	71.71
Outstanding at September 30, 2023	0.8	$	68.34	0.7	$	75.54
Granted	0.3	$	92.30	0.2	$	104.66
PEP units earned (unearned)	—	$	—	0.2	$	52.50
Vested	(0.3)	$	50.14	(0.4)	$	52.50
Cancelled	0.0	$	77.32	—	$	89.76
Outstanding at September 30, 2024	0.8	$	83.96	0.7	$	95.38
Granted	0.2	$	110.65	0.2	$	129.28
PEP units earned (unearned)	—	$	—	0.1	$	85.46
Vested	(0.2)	$	75.72	(0.3)	$	85.46
Cancelled	(0.1)	$	95.85	(0.1)	$	109.53
Outstanding at September 30, 2025	0.7	$	95.64	0.6	$	109.74

Derivative Financial Instruments and Fair Value Measurements - Schedule of Notional Principle, Fixed Rates and Expiration Dates of Outstanding Interest Rate Swap Agreements (Details) - Interest Rate Swap - Cash Flow Hedging - Designated as Hedging Instrument - USD ($) $ in Millions	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2021
Derivative [Line Items]
Notional Amount			$ 400.0
Fixed Rate (as percent)			1.283%
February 2023 \| USD
Derivative [Line Items]
Notional Amount	$ 400.0	$ 400.0
Fixed Rate (as percent)	1.283%	1.283%

Pension Benefit Obligations - Schedule of Reconciliations of Changes In Fair Value of Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Change in plan assets
Fair value of plan assets at beginning of year	$ 913.3
Employer contributions	2.7	$ 2.5
Fair value of plan assets at end of year		913.3
U.S.
Change in plan assets
Fair value of plan assets at beginning of year	109.0	98.8	$ 101.4
Actual return on plan assets	3.0	15.8	7.8
Employer contributions	10.6	11.9	8.2
Participant contributions	0.1	0.1	0.1
Benefits and expenses paid	(17.1)	(17.6)	(17.2)
Plan settlements	(0.7)	0.0	(1.5)
Foreign currency translation gain	0.0	0.0	0.0
Fair value of plan assets at end of year	104.9	109.0	98.8
Int’l
Change in plan assets
Fair value of plan assets at beginning of year	804.3	673.3	683.5
Actual return on plan assets	(15.1)	89.0	(54.2)
Employer contributions	23.7	25.1	24.8
Participant contributions	0.2	0.3	0.2
Benefits and expenses paid	(46.2)	(47.7)	(42.2)
Plan settlements	0.0	(3.2)	(1.5)
Foreign currency translation gain	5.0	67.5	62.7
Fair value of plan assets at end of year	$ 771.9	$ 804.3	$ 673.3

Earnings Per Share (Details) - shares shares in Thousands	12 Months Ended
Earnings Per Share (Details) - shares shares in Thousands	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Earnings Per Share [Abstract]
Denominator for basic earnings per share (in shares)	132,373	135,544	138,614
Potential common shares (in shares)	900	1,000	1,500
Denominator for diluted earnings per share (in shares)	133,311	136,453	140,109

Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2025	Sep. 30, 2024
Statement of Financial Position [Abstract]
Common stock, shares authorized (in shares)	300,000,000	300,000,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares issued (in shares)	131,782,371	132,552,407
Common stock, shares outstanding (in shares)	131,782,371	132,552,407

Income Taxes (Tables)

12 Months Ended

Sep. 30, 2025

Income Tax Disclosure [Abstract]

Schedule of Income Tax Expense

Income tax expense was comprised of:


	Fiscal Year Ended
	September 30, 2025		September 30, 2024		September 30, 2023

	(in millions)
Current:
Federal	$	88.9	$	15.1	$	67.7
State	26.4		(78.6)		71.9
Foreign	56.1		63.5		52.8
Total current income tax expense	171.4		—		192.4
Deferred:
Federal	7.7		45.2		(71.8)
State	(6.5)		68.1		(84.3)
Foreign	31.4		39.6		19.8
Total deferred income tax expense (benefit)	32.6		152.9		(136.3)
Total income tax expense	$	204.0	$	152.9	$	56.1

Schedule of Difference Between Federal Statutory Rate and the Effective Tax Rate

The major elements contributing to the difference between the U.S. federal statutory rate of 21% for fiscal years ended September 30, 2025, 2024 and 2023 and the effective tax rate are as follows:


	Fiscal Year Ended
	September 30, 2025				September 30, 2024				September 30, 2023
	Amount		%		Amount		%		Amount		%

	(in millions)
Tax at federal statutory rate	$	192.3	21.0	%	$	150.8	21.0	%	$	44.8	21.0	%
State income tax, net of federal benefit	16.1		1.8		(8.5)		(1.2)		(7.1)		(3.3)
Change in uncertain tax positions	46.7		5.1		18.6		2.6		9.4		4.4
Foreign residual income	41.9		4.6		43.8		6.1		59.4		27.8
Nondeductible costs	16.6		1.8		20.6		2.9		10.7		5.0
Tax rate changes	2.3		0.3		1.2		0.2		(3.2)		(1.5)
Audit settlement	1.4		0.1		0.5		0.1		1.9		0.9
Income tax credits and incentives	(59.5)		(6.5)		(63.5)		(8.8)		(68.2)		(31.9)
Legal entity restructuring	(20.1)		(2.2)		—		—		—		—
Exclusion of tax on non-controlling interests	(15.6)		(1.7)		(12.5)		(1.7)		(9.4)		(4.4)
Valuation allowance	(11.8)		(1.3)		(12.6)		(1.8)		16.6		7.8
Tax exempt income	(2.1)		(0.2)		(2.5)		(0.4)		(3.3)		(1.5)
Foreign tax rate differential	(1.1)		(0.1)		(2.8)		(0.4)		0.2		0.1
Return to provision	(0.5)		(0.1)		(3.7)		(0.5)		(0.5)		(0.2)
ACAP investment sale	—		—		20.2		2.8		—		—
Other items, net	(2.6)		(0.3)		3.3		0.4		4.8		2.1
Total income tax expense	$	204.0	22.3	%	$	152.9	21.3	%	$	56.1	26.3	%

Schedule of Deferred Tax Assets (liabilities)

The deferred tax assets (liabilities) are as follows:


	Fiscal Year Ended
	September 30, 2025		September 30, 2024

	(in millions)
Deferred tax assets:
Compensation and benefit accruals not currently deductible	$	81.8	$	85.4
Net operating loss carryforwards	99.2		107.5
Self-insurance reserves	66.6		38.3
Research and experimentation and other tax credits	34.3		67.1
Pension liability	23.5		34.9
Accrued liabilities	263.3		265.7
Capital loss carryforward	13.0		49.5
Partnership investment	15.5		22.3
Other	12.2		8.2
Total deferred tax assets	609.4		678.9
Deferred tax liabilities:
Unearned revenue	(31.0)		(4.1)
Depreciation and amortization	(58.9)		(83.7)
Acquired intangible assets	(39.6)		—
Investment in subsidiaries	(9.8)		(9.9)
Right of use assets	(82.4)		(85.2)
Contingent consideration	—		(30.5)
Other	(3.3)		(5.4)
Total deferred tax liabilities	(225.0)		(218.8)
Valuation allowance	(157.1)		(160.9)
Net deferred tax assets	$	227.3	$	299.2

Schedule of Reconciliation of Unrecognized Tax Benefits

A reconciliation of the beginning and ending amount of gross unrecognized tax benefits is as follows:


	Fiscal Year Ended
	September 30, 2025		September 30, 2024

	(in millions)
Balance at the beginning of the year	$	81.3	$	62.1
Gross increase in current period’s tax positions	9.2		34.5
Gross increase in prior years’ tax positions	47.0		13.9
Gross decrease in prior years’ tax positions	(6.4)		(20.1)
Decrease due to settlement with tax authorities	—		(7.4)
Decrease due to lapse of statute of limitations	(1.3)		(2.2)
Gross change due to foreign exchange fluctuations	(0.2)		0.5
Balance at the end of the year	$	129.6	$	81.3

Derivative Financial Instruments and Fair Value Measurements

12 Months Ended

Sep. 30, 2025

Derivative Financial Instruments and Fair Value Measurements [Abstract]

Derivative Financial Instruments and Fair Value Measurements

The Company uses interest rate derivative contracts to hedge interest rate exposures on the Company’s variable rate debt. The Company enters into foreign currency derivative contracts with financial institutions to reduce the risk that its cash flows and earnings will be adversely affected by foreign currency exchange rate fluctuations. The Company’s hedging program is not designated for trading or speculative purposes.

The Company recognizes derivative instruments as either assets or liabilities on the accompanying consolidated balance sheets at fair value. The Company records changes in the fair value (i.e., gains or losses) of the derivatives that have been designated as accounting hedges in the accompanying consolidated statements of operations as interest expense or to accumulated other comprehensive loss in the accompanying consolidated balance sheets.

Cash Flow Hedges

The Company uses interest rate swap and interest rate cap agreements designated as cash flow hedges to limit exposure to variable interest rates on portions of the Company’s debt. The Company initially reports any gain on the effective portion of a cash flow hedge as a component of accumulated other comprehensive loss. Depending on the type of cash flow hedge, the gain is subsequently reclassified against interest expense when the interest expense on the variable rate debt is recognized. If the hedged transaction becomes probable of not occurring, any gain or loss related to interest rate swap or interest rate cap agreements would be recognized in other income.

The notional principal, fixed rates and related effective and expiration dates of the Company’s outstanding interest rate swap agreements were as follows:

September 30, 2025

Notional Amount
Currency

Notional Amount
(in millions)

Fixed
Rate

Effective
Date

Expiration
Date

USD

400.0

1.283%

February 2023

March 2028

September 30, 2024

Notional Amount
Currency

Notional Amount
(in millions)

Fixed
Rate

Effective
Date

Expiration
Date

USD

400.0

1.283%

February 2023

March 2028

In the fourth quarter of fiscal 2021, the Company entered into interest rate swap agreements with a notional value of $400.0 million to manage the interest rate exposure of its variable rate loans. The swaps became effective February 2023 and terminate in March 2028. By entering into the swap agreements, the Company converted a portion of the SOFR rate-based liability into a fixed-rate liability. The Company will pay a fixed rate of 1.283% and receive payment at the prevailing one-month SOFR.

In the third quarter of fiscal 2022, the Company purchased interest rate cap agreements with a notional value of $300.0 million to manage interest rate exposure of its variable rate loans. The caps became effective on June 30, 2022 and terminate in March 2028. The caps reduce the Company’s exposure to one-month SOFR. In the event one-month SOFR exceeds 3.465%, the Company will pay the spread between prevailing one-month SOFR and 3.465%.

See Note 17 for accumulated balances and reporting period activities of derivatives related to reclassifications out of accumulated other comprehensive loss for the years ended September 30, 2025, 2024 and 2023. Additionally, there were no material losses recognized in income due to amounts excluded from effectiveness testing from the Company’s interest rate swap agreements.

Other Foreign Currency Forward Contracts

The Company uses foreign currency forward contracts which are not designated as accounting hedges to hedge intercompany transactions and other monetary assets or liabilities denominated in currencies other than the functional currency of a subsidiary. Gains and losses on these contracts were not material for the years ended September 30, 2025, 2024 and 2023.

Fair Value Measurements

The fair values of the interest rate swap and interest rate cap agreements were derived by taking the net present value of the expected cash flows using observable market inputs (Level 2) such as SOFR rate curves, futures, volatilities and basis spreads (when applicable).

As discussed in Note 3, the Company received an equity investment in the civil infrastructure construction business buyer and concurrently participated as a member of a lending group in a revolving credit facility. The Company elected the fair value option for its equity investment due to the availability of quoted prices of identical assets. The fair value option was also elected for the credit facility investment. Changes in fair value of both investments are classified within other income on the consolidated statements of operations. The Company records interest income at the stated coupon rate of the credit facility and classifies it within interest income on the consolidated statement of operations. Fair value for the equity investment is determined using Level 1 inputs, and fair value of the credit facility investment is determined using Level 3 inputs, such as estimated cash flows and estimated discount rates. The Company recorded a gain of $2.5 million and $7.2 million in other income during the years ended September 30, 2025 and September 30, 2024, respectively, representing the increase in fair value of these investments.

In the fourth quarter of fiscal 2025, the Company issued contingent consideration in connection with the acquisition of a business, with a maximum value of $17.7 million. The contingent consideration is a liability that is measured at fair value with changes in fair value reported through earnings. The contingent consideration is measured using Level 2 inputs, such as quoted market prices and volatilities.

Below are the Company’s non-pension financial assets and liabilities recorded at fair value on a recurring basis within the ASC 820-10 fair value hierarchy:


	As of September 30, 2025
	Balance Sheet Location	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Total Fair Value

	(in millions)
Interest rate contracts	Other current assets	$	—	$	9.0	$	—	$	9.0
Interest rate contracts	Other non-current assets	—		10.0		—		10.0
Interest rate contracts	Other current liabilities	—		(1.8)		—		(1.8)
Interest rate contracts	Other long-term liabilities	—		(2.8)		—		(2.8)
Credit facility investment	Other non-current assets	—		—		17.4		17.4
Contingent Consideration	Other long-term liabilities	—		(7.5)		—		(7.5)
Equity investment	Other non-current assets	21.9		—		—		21.9
Total net assets at fair value		$	21.9	$	6.9	$	17.4	$	46.2


	As of September 30, 2024
	Balance Sheet Location	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Total Fair Value

	(in millions)
Interest rate contracts	Other current assets	$	—	$	9.2	$	—	$	9.2
Interest rate contracts	Other non-current assets	—		16.5		—		16.5
Interest rate contracts	Other current liabilities	—		(0.9)		—		(0.9)
Interest rate contracts	Other long-term liabilities	—		(3.6)		—		(3.6)
Credit facility investment	Other non-current assets	—		—		21.9		21.9
Equity investment	Other non-current assets	19.4		—		—		19.4
Total net assets at fair value		$	19.4	$	21.2	$	21.9	$	62.5

The table below sets forth a summary of changes in the fair value of the Company’s Level 3 investment assets:


	Year-ended September 30, 2025
	Beginning Balance		Investment Gains/(Losses)	Interest Earned	Loans	Collections	Ending Balance

	(in millions)
Credit facility investment including accrued interest	$	21.9	0.1	1.1	19.0	(24.7)	$	17.4


	Year-ended September 30, 2024
	Beginning Balance		Investment Gains/(Losses)	Interest Earned	Loans	Collections	Ending Balance
	(in millions)
Credit facility investment including accrued interest	$	—	0.5	0.5	32.5	(11.6)	$	21.9

- Definition

The entire disclosure for derivative instruments and hedging activities including, but not limited to, risk management strategies, non-hedging derivative instruments, assets, liabilities, revenue and expenses, and methodologies and assumptions used in determining the amounts.

+ References

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+ Details

Debt - Other Debt and Other Items (Details) - Other Debt - USD ($) $ in Millions	Sep. 30, 2025	Sep. 30, 2024
Unsecured
Debt Instrument [Line Items]
Current borrowing capacity	$ 367.4
Standby Letters of Credit
Debt Instrument [Line Items]
Outstanding standby letters of credit	$ 899.4	$ 934.5

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
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+ Details

Discontinued Operations, Goodwill and Intangible Assets

12 Months Ended

Sep. 30, 2025

Discontinued Operations, Goodwill, and Intangible Assets [Abstract]

Discontinued Operations, Goodwill and Intangible Assets

In the first quarter of fiscal 2020, management approved a plan to dispose of via sale the Company’s self-perform at-risk construction businesses. These businesses include the Company’s civil infrastructure, power, and oil and gas construction businesses that were previously reported in the Company’s Construction Services segment. After consideration of the relevant facts, the Company concluded the assets and liabilities of its self-perform at-risk construction businesses met the criteria for classification as held for sale. The Company concluded the actual and proposed disposal activities represented a strategic shift that would have a major effect on the Company’s operations and financial results and qualified for presentation as discontinued operations in accordance with FASB ASC 205-20. Accordingly, the financial results of the self-perform at-risk construction businesses are presented in the Consolidated Statement of Operations as discontinued operations for all periods presented. Current and non-current assets and liabilities of these businesses not sold as of the balance sheet date are presented in the Consolidated Balance Sheets as assets and liabilities held for sale for both periods presented.

The Company completed the sale of its power and oil and gas construction businesses in fiscal 2021 and fiscal 2022, respectively. The Company completed the sale of its civil infrastructure construction business to affiliates of Oroco Capital in the second quarter of fiscal 2021. In the second quarter of fiscal 2024, the Company recorded a $103.1 million loss related to a revised estimate of its contingent consideration receivable recognized in its civil infrastructure construction business.

During the third quarter of fiscal 2024, the Company resolved contingencies related to the sale of its civil infrastructure construction business and received equity in the counterparty, and the Company recorded a $12.7 million gain based on the fair value of the equity received. Concurrently, the Company participated as a member of a lending group in a revolving credit facility for the counterparty, committing to fund $30 million that matures in May 2029. At September 30, 2025, the counterparty had $15.4 million outstanding under the credit facility, and all cash flows were classified as other investing activities.

During the second quarter of fiscal 2025, the Company and its joint venture counterparty amended the joint venture agreement for a business classified as held for sale. In connection with the amendment and consistent with ASC 810, Consolidation, the Company reconsidered whether it remained the primary beneficiary under the variable interest model and concluded it was no longer the primary beneficiary. As such, the Company deconsolidated the joint venture as of the amendment date. The Company continues to present its retained noncontrolling interest as held for sale and equity in earnings from the joint venture are reported in net loss from discontinued operations. No gain or loss was recognized in the deconsolidation of the joint venture during the second quarter of fiscal 2025.

Department of Energy Deactivation, Demolition, and Removal Project

A former affiliate of the Company, Amentum Environment & Energy, Inc., f/k/a AECOM Energy and Construction, Inc. (“Former Affiliate”), executed a cost-reimbursable task order with the Department of Energy (DOE) in 2007 to provide deactivation, demolition and removal services at a New York State project site that, during 2010, experienced contamination and performance issues. In February 2011, the Former Affiliate and the DOE executed a Task Order Modification that changed some cost-reimbursable contract provisions to at-risk. The Task Order Modification, including subsequent amendments, required the DOE to pay all project costs up to $106 million, required the Former Affiliate and the DOE to equally share in all project costs incurred from $106 million to $146 million, and required the Former Affiliate to pay all project costs exceeding $146 million.

Due to unanticipated requirements and permitting delays by federal and state agencies, as well as delays and related ground stabilization activities caused by Hurricane Irene in 2011, the Former Affiliate was required to perform work outside the scope of the Task Order Modification. In December 2014, the Former Affiliate submitted an initial set of claims against the DOE pursuant to the Contracts Disputes Acts seeking recovery of $103 million, including additional fees on changed work scope (the “2014 Claims”). On December 6, 2019, the Former Affiliate submitted a second set of claims against the DOE seeking recovery of an additional $60.4 million, including additional project costs and delays outside the scope of the contract as a result of differing site and ground conditions (the “2019 Claims”). The Former Affiliate also submitted three alternative breach of contract claims to the 2014 Claims and the 2019 Claims that may entitle the Former Affiliate to recovery of $148.5 million to $329.4 million. On December 30, 2019, the DOE denied the Former Affiliate’s 2014 Claims. On September 25, 2020, the DOE denied the Former Affiliate’s 2019 Claims. The Company filed an appeal of these decisions on December 20, 2020 in the Court of Federal Claims. Deconstruction, decommissioning and site restoration activities are complete.

On January 31, 2020, the Company completed the sale of its Management Services business, including the Former Affiliate who worked on the DOE project, to Maverick Purchaser Sub LLC (“MS Purchaser”), an affiliate of American Securities LLC and Lindsay Goldberg LLC. The Company and the MS Purchaser agreed that all future DOE project claim recoveries and costs will be split 10% to the MS Purchaser and 90% to the Company with the Company retaining control of all future strategic legal decisions.

Fact discovery has concluded and expert discovery will proceed once the stay due to the government shutdown is lifted, expected in fiscal year 2026. The Company intends to vigorously pursue all claimed amounts but can provide no certainty that the Company will recover 2014 Claims and 2019 Claims submitted against the DOE, or any additional incurred claims or costs, which could have a material adverse effect on the Company’s results of operations.

Refinery Turnaround Project

A former affiliate of the Company, which was sold in a series of transactions to effectuate the sale of the self‑perform at-risk construction businesses, entered into an agreement to perform turnaround maintenance services in Montana in December 2017. The former affiliate performed additional work outside of the original contract and became entitled to payment from the refinery owner. As part of the sale of the former affiliate, the refinery turnaround project, including related claims, were retained by the Company. The former affiliate's claims against the refinery owner and the refinery owner's crossclaims against the Company's former affiliate moved to federal court. A jury trial was completed on

February 1, 2025, resulting in a favorable verdict for the Company. As a result of unfavorable court orders on post-trial motions during the third quarter of fiscal 2025, including pre-judgment interest and prompt payment interest, and issuance of the associated judgment, the Company recorded a $53.0 million loss from the reduction in the expected future net cash proceeds the Company would receive as a result of the trial verdict. The Company has appealed the judgment. The loss is reported in discontinued operations as the project was completed prior to the sale of the former affiliate.

The following table represents summarized balance sheet information of assets and liabilities held for sale (in millions):


	September 30, 2025		September 30, 2024
Cash and cash equivalents	$	—	$	4.0
Receivables and contract assets	—		73.2
Current assets held for sale	$	—	$	77.2

Investment in unconsolidated joint venture	$	18.9	$	—
Property and equipment, net	$	—	$	16.7
Other	0.1		1.2
Write-down of assets to fair value less cost to sell	—		(17.9)
Non-current assets held for sale	$	19.0	$	—

Accounts payable and accrued expenses	$	—	$	35.6
Current liabilities held for sale	$	—	$	35.6
Long-term liabilities held for sale	$	—	$	—

The following table represents summarized income statement information of discontinued operations (in millions):


	Fiscal Year Ended
	September 30, 2025		September 30, 2024		September 30, 2023
Revenue	$	97.6	$	178.2	$	212.8
Cost of revenue	101.4		181.1		223.2
Gross loss	(3.8)		(2.9)		(10.4)
Equity in losses of joint ventures	(10.1)		(3.4)		(2.9)
Loss on disposal activities	(83.8)		(97.1)		(50.6)
Transaction costs	—		(0.2)		(0.2)
Loss from operations	(97.7)		(103.6)		(64.1)
Other expense	(0.3)		(1.5)		(1.0)
Loss before taxes	(98.0)		(105.1)		(65.1)
Income tax benefit	(22.6)		(0.1)		(7.9)
Net loss from discontinued operations	$	(75.4)	$	(105.0)	$	(57.2)

The significant components included in the Consolidated Statement of Cash Flows for the discontinued operations are as follows (in millions):


	Fiscal Year Ended
	September 30, 2025		September 30, 2024		September 30, 2023
Payments for capital expenditures	$	—	$	(2.5)	$	(6.2)
Noncash increase in noncurrent assets held for sale due to deconsolidation of a joint venture	$	41.6	$	—	$	—
Noncash decrease in noncontrolling interest due to deconsolidation of a joint venture	$	(13.8)	$	—	$	—

The Company also recorded a $12.7 million non-cash gain in discontinued operations in fiscal 2024.

The Company completed two business acquisitions during the year ended September 30, 2025 for total consideration of $375.9 million, which included stock consideration of $146.4 million. Neither of these two acquisitions met the quantitative thresholds to require separate disclosure. The Company acquired these businesses to expand its competitive advantage and compound strengths to achieve its long-term profitability targets. The Company preliminarily estimates the amount of identifiable assets acquired based on the facts and circumstances available at the time of acquisition. The Company determines the final value of the identifiable intangible assets as soon as information is available, but not more than 12 months from the date of acquisition. The initial accounting for these acquisitions is not complete as of September 30, 2025 as the Company continues to assess the value of the acquired intellectual property intangible asset.

The changes in the carrying value of goodwill by reportable segment for the year ended September 30, 2025 were as follows:


	September 30, 2024		Foreign Exchange Impact		Acquired		September 30, 2025

	(in millions)
Americas	$	2,625.7	$	(5.4)	$	150.1	$	2,770.4
International	854.5		0.4		75.3		930.2
Total	$	3,480.2	$	(5.0)	$	225.4	$	3,700.6


	September 30, 2025						September 30, 2024
	Gross Amount		Accumulated Amortization		Intangible Assets, Net		Gross Amount		Accumulated Amortization		Intangible Assets, Net		Amortization Period

	(in millions)												(years)
Backlog and Customer relationships	$	7.4	$	(2.5)	$	4.9	$	671.7	$	(664.8)	$	6.9	1 - 11
Intellectual property	178.4		—		178.4		—		—		—		5
Total	$	185.8	$	(2.5)	$	183.3	$	671.7	$	(664.8)	$	6.9

Amortization expense of acquired intangible assets included within cost of revenue was $1.5 million and $18.8 million for the years ended September 30, 2025 and 2024, respectively. The following table presents estimated amortization expense of existing intangible assets for the succeeding years:


Fiscal Year	(in millions)
2026	$	37.2
2027	37.2
2028	37.2
2029	36.0
2030	35.7
Total	$	183.3

Revenue Recognition

12 Months Ended

Sep. 30, 2025

Revenue from Contract with Customer [Abstract]

Revenue Recognition

The Company follows accounting principles for recognizing revenue upon the transfer of control of promised goods or services to customers, in an amount that reflects the expected consideration received in exchange for those goods or services. The Company generally recognizes revenues over time as performance obligations are satisfied. The Company generally measures its progress to completion using an input measure of total costs incurred divided by total costs expected to be incurred, which it believes to be the best measure of progress towards completion of the performance obligation. In the course of providing its services, the Company routinely subcontracts for services and incurs other direct costs on behalf of its clients. These costs are passed through to clients and, in accordance with GAAP, are included in the Company’s revenue and cost of revenue. These pass-through revenues for the years ended September 30, 2025, 2024 and 2023 were $8.6 billion, $8.9 billion and $7.7 billion, respectively.

Recognition of revenue and profit is dependent upon a number of factors, including the accuracy of a variety of estimates made at the balance sheet date, such as engineering progress, material quantities, the achievement of milestones, penalty provisions, labor productivity and cost estimates. Additionally, the Company is required to make estimates for the amount of consideration to be received, including bonuses, awards, incentive fees, claims, unpriced change orders, penalties, and liquidated damages. Variable consideration is included in the estimate of the transaction price only to the extent that a significant reversal would not be probable. Management continuously monitors factors that may affect the quality of its estimates, and material changes in estimates are disclosed accordingly. Costs attributable to claims are treated as costs of contract performance as incurred.

The following summarizes the Company’s major contract types:

Cost Reimbursable Contracts

Cost reimbursable contracts include cost-plus fixed fee, cost-plus fixed rate, and time-and-materials price contracts. Under cost-plus contracts, the Company charges clients for its costs, including both direct and indirect costs, plus a negotiated fee or rate. The Company recognizes revenue based on actual direct costs incurred and the applicable fixed rate or portion of the fixed fee earned as of the balance sheet date. Under time-and-materials price contracts, the Company negotiates hourly billing rates and charges its clients based on the actual time that it expends on a project. In addition, clients reimburse the Company for materials and other direct incidental expenditures incurred in connection with its performance under the contract. The Company may apply a practical expedient to recognize revenue in the amount in which it has the right to invoice if its right to consideration is equal to the value of performance completed to date.

Guaranteed Maximum Price Contracts (GMP)

GMP contracts share many of the same contract provisions as cost-plus and fixed-price contracts. As with cost-plus contracts, clients are provided a disclosure of all the project costs, and a lump sum or percentage fee is separately identified. The Company provides clients with a guaranteed price for the overall project (adjusted for change orders issued by clients) and a schedule including the expected completion date. Cost overruns or costs associated with project delays in completion could be the Company’s responsibility. For many of the Company’s GMP contracts, the final price is generally not established until the Company has subcontracted a substantial percentage of the trade contracts with terms consistent with the master contract, and it has negotiated additional contractual limitations, such as waivers of consequential damages as well as aggregate caps on liabilities and liquidated damages. Revenue is recognized for GMP contracts as project costs are incurred relative to total estimated project costs.

Fixed-Price Contracts

Fixed-price contracts include both lump-sum and fixed-unit price contracts. Under lump-sum contracts, the Company performs all the work under the contract for a specified fee. Lump-sum contracts are typically subject to price adjustments if the scope of the project changes or unforeseen conditions arise. Under fixed-unit price contracts, the Company performs a number of units of work at an agreed price per unit with the total payment under the contract determined by the actual number of units delivered. Revenue is recognized for fixed-price contracts using the input method measured on a cost-to-cost basis as the Company believes this is the best measure of progress towards completion.

Disaggregated Revenue

The following tables present the Company’s revenues disaggregated by revenue sources:


	Fiscal Year Ended
	September 30, 2025		September 30, 2024		September 30, 2023

	(in millions)
Cost reimbursable	$	6,196.1	$	6,361.4	$	6,128.8
Guaranteed maximum price	5,960.7		6,030.0		4,887.7
Fixed price	3,982.8		3,714.1		3,362.0
Total revenue	$	16,139.6	$	16,105.5	$	14,378.5


	Fiscal Year Ended
	September 30, 2025		September 30, 2024		September 30, 2023

	(in millions)
Americas	$	12,526.4	$	12,487.0	$	10,976.4
Europe, Middle East, India, Africa	2,153.3		2,141.5		1,937.3
Asia-Australia-Pacific	1,459.9		1,477.0		1,464.8
Total revenue	$	16,139.6	$	16,105.5	$	14,378.5

Remaining Unsatisfied Performance Obligations

As of September 30, 2025, the Company had allocated $19.7 billion of transaction price to unsatisfied or partially satisfied performance obligations, of which approximately 57% is expected to be satisfied within the next twelve months. The majority of remaining performance obligation after the first 12 months are expected to be recognized over a two-year period.

Contract liabilities represent billings as of the balance sheet date, as allowed under the terms of a contract, but not yet recognized as contract revenue pursuant to the Company’s revenue recognition policy. The Company recognized revenue of $918.9 million and $801.0 million during the years ended September 30, 2025 and 2024, respectively, that was included in contract liabilities as of September 30, 2024 and 2023, respectively.

The Company’s timing of revenue recognition may not be consistent with its rights to bill and collect cash from its clients. Those rights are generally dependent upon advance billing terms, milestone billings based on the completion of certain phases of work or when services are performed. The Company’s accounts receivables represent amounts billed to clients that have yet to be collected and represent an unconditional right to cash from its clients. Contract assets represent the amount of contract revenue recognized but not yet billed pursuant to contract terms or accounts billed after the balance sheet date.

Net accounts receivable consisted of the following:


	Fiscal Year Ended
	September 30, 2025		September 30, 2024

	(in millions)
Billed	$	1,934.3	$	2,184.9
Contract retentions	647.6		696.3
Total accounts receivable—gross	2,581.9		2,881.2
Allowance for doubtful accounts and credit losses	(84.8)		(87.9)
Total accounts receivable—net	$	2,497.1	$	2,793.3

Substantially all contract assets as of September 30, 2025 and September 30, 2024 are expected to be billed and collected within twelve months, except for claims. Significant claims recorded in contract assets and other non-current assets were approximately $400 million and $180 million as of September 30, 2025 and 2024, respectively. The asset related to the Deactivation, Demolition, and Removal Project retained from the MS Purchaser as defined and and discussed in Note 3 is presented in other non-current assets from continuing operations in the Consolidated Balance Sheet. Contract retentions represent amounts invoiced to clients where payments have been withheld from progress payments until the contracted work has been completed and approved by the client but nonetheless represent an unconditional right to cash.

The Company considers a broad range of information to estimate expected credit losses including the related ages of past due balances, projections of credit losses based on historical trends, and collection history and credit quality of its clients. Negative macroeconomic trends or delays in payment of outstanding receivables could result in an increase in the estimated credit losses.

No single client accounted for more than 10% of the Company’s outstanding receivables at September 30, 2025 and 2024.

The Company sold trade receivables to financial institutions, of which $268.2 million and $319.5 million were outstanding as of September 30, 2025 and 2024, respectively. The Company does not retain financial or legal obligations for these receivables that would result in material losses. The Company’s ongoing involvement is limited to the remittance of customer payments to the financial institutions with respect to the sold trade receivables.

- Definition

The entire disclosure of revenue from contract with customer to transfer good or service and to transfer nonfinancial asset. Includes, but is not limited to, disaggregation of revenue, credit loss recognized from contract with customer, judgment and change in judgment related to contract with customer, and asset recognized from cost incurred to obtain or fulfill contract with customer. Excludes insurance and lease contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-7

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-9

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-10

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 15
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-15

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-12

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-12

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-12

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-12

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-12

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-13

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Name Accounting Standards Codification
-Topic 606
-Publisher FASB
-URI https://asc.fasb.org/606/tableOfContent

+ Details

Pension Benefit Obligations - Schedule of Underlying Assumptions for the Pension Plans (Details)	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
U.S.
Weighted-average assumptions to determine benefit obligation:
Discount rate (as percent)	5.01%	4.73%	5.76%
Weighted-average assumptions to determine net periodic benefit cost:
Discount rate (as percent)	4.73%	5.76%	5.40%
Expected long-term rate of return on plan assets (as percent)	6.25%	6.90%	7.00%
Int’l
Weighted-average assumptions to determine benefit obligation:
Discount rate (as percent)	5.83%	5.04%	5.65%
Salary increase rate (as percent)	2.81%	2.91%	3.06%
Weighted-average assumptions to determine net periodic benefit cost:
Discount rate (as percent)	5.04%	5.65%	5.27%
Salary increase rate (as percent)	2.91%	3.06%	3.48%
Expected long-term rate of return on plan assets (as percent)	5.51%	5.74%	6.04%

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Total AECOM Stockholders’ Equity	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Accumulated Deficits	Non- Controlling Interests
Beginning balance at Sep. 30, 2022	$ 2,605,379	$ 2,476,654	$ 1,389	$ 4,156,594	$ (979,675)	$ (701,654)	$ 128,725
Increase (Decrease) in Stockholders' Equity
Net income	100,141	55,332				55,332	44,809
Dividends declared	(100,872)	(100,872)				(100,872)
Other comprehensive loss	53,166	53,098			53,098		68
Issuance of stock	64,983	64,983	19	64,964
Repurchases of stock	(382,745)	(382,745)	(46)	(25,917)		(356,782)
Stock-based compensation	45,882	45,882		45,882
Contributions from noncontrolling interests	17,225						17,225
Distributions to noncontrolling interests	(19,448)						(19,448)
Ending balance at Sep. 30, 2023	2,383,711	2,212,332	1,362	4,241,523	(926,577)	(1,103,976)	171,379
Increase (Decrease) in Stockholders' Equity
Net income	460,255	402,266				402,266	57,989
Dividends declared	(120,454)	(120,454)				(120,454)
Other comprehensive loss	44,113	43,906			43,906		207
Issuance of stock	65,385	65,385	16	65,369
Repurchases of stock	(480,750)	(480,750)	(52)	(21,215)		(459,483)
Stock-based compensation	61,520	61,520		61,520
Contributions from noncontrolling interests	13,508						13,508
Distributions to noncontrolling interests	(56,878)						(56,878)
Ending balance at Sep. 30, 2024	2,370,410	2,184,205	1,326	4,347,197	(882,671)	(1,281,647)	186,205
Increase (Decrease) in Stockholders' Equity
Net income	636,187	561,774				561,774	74,413
Dividends declared	(139,303)	(139,303)				(139,303)
Other comprehensive loss	(10,387)	(10,356)			(10,356)		(31)
Issuance of stock	219,013	219,013	25	218,988
Repurchases of stock	(384,188)	(384,188)	(33)	(18,498)		(365,657)
Stock-based compensation	61,439	61,439		61,439
Effect of deconsolidation of a joint venture	(13,768)						(13,768)
Contributions from noncontrolling interests	2,450						2,450
Distributions to noncontrolling interests	(45,669)						(45,669)
Ending balance at Sep. 30, 2025	$ 2,696,184	$ 2,492,584	$ 1,318	$ 4,609,126	$ (893,027)	$ (1,224,833)	$ 203,600

Reclassifications out of Accumulated Other Comprehensive Loss (Tables)

12 Months Ended

Sep. 30, 2025

Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]

Schedule of Accumulated Balances and Reporting Period Activities Related to Reclassifications Out of Accumulated Other Comprehensive Loss


	Pension Related Adjustments		Foreign Currency Translation Adjustments		Loss on Derivative Instruments		Accumulated Other Comprehensive Loss
Balances at September 30, 2022	$	(217.3)	$	(799.3)	$	36.9	$	(979.7)
Other comprehensive income (loss) before reclassification	(10.9)		59.6		10.7		59.4
Amounts reclassified from accumulated other comprehensive loss	2.2		—		(8.5)		(6.3)
Balances at September 30, 2023	$	(226.0)	$	(739.7)	$	39.1	$	(926.6)


	Pension Related Adjustments		Foreign Currency Translation Adjustments		Loss on Derivative Instruments		Accumulated Other Comprehensive Loss
Balances at September 30, 2023	$	(226.0)	$	(739.7)	$	39.1	$	(926.6)
Other comprehensive (loss) income before reclassification	(26.6)		93.2		(10.6)		56.0
Amounts reclassified from accumulated other comprehensive loss	0.6		—		(12.7)		(12.1)
Balances at September 30, 2024	$	(252.0)	$	(646.5)	$	15.8	$	(882.7)


	Pension Related Adjustments		Foreign Currency Translation Adjustments		Loss on Derivative Instruments		Accumulated Other Comprehensive Loss
Balances at September 30, 2024	$	(252.0)	$	(646.5)	$	15.8	$	(882.7)
Other comprehensive (loss) income before reclassification	(1.3)		(5.9)		4.8		(2.4)
Amounts reclassified from accumulated other comprehensive loss	1.9		—		(9.8)		(7.9)
Balances at September 30, 2025	$	(251.4)	$	(652.4)	$	10.8	$	(893.0)

Audit Information	12 Months Ended
Audit Information	Sep. 30, 2025
Audit Information [Abstract]
Auditor Firm ID	42
Auditor Name	Ernst & Young LLP
Auditor Location	Dallas, Texas

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Statement of Comprehensive Income [Abstract]
Net income	$ 636,187	$ 460,255	$ 100,141
Other comprehensive (loss) income, net of tax:
Net unrealized (loss) gain on derivatives, net of tax	(5,051)	(23,290)	2,165
Foreign currency translation adjustments	(5,937)	93,389	59,720
Pension adjustments, net of tax	601	(25,986)	(8,719)
Other comprehensive (loss) income, net of tax	(10,387)	44,113	53,166
Comprehensive income, net of tax	625,800	504,368	153,307
Noncontrolling interests in comprehensive income of consolidated subsidiaries, net of tax	(74,382)	(58,196)	(44,877)
Comprehensive income attributable to AECOM, net of tax	$ 551,418	$ 446,172	$ 108,430

Debt - Schedule of Maturities of Debt (Details) - USD ($) $ in Millions	Sep. 30, 2025	Sep. 30, 2024
Debt Disclosure [Abstract]
2026	$ 66.3
2027	31.2
2028	22.1
2029	761.3
2030	6.8
Thereafter	1,856.0
Total	$ 2,743.7	$ 2,539.8

Derivative Financial Instruments and Fair Value Measurements (Tables)

12 Months Ended

Sep. 30, 2025

Derivative Financial Instruments and Fair Value Measurements [Abstract]

Schedule of Notional Principle, Fixed Rates and Expiration Dates of Outstanding Interest Rate Swap Agreements

The notional principal, fixed rates and related effective and expiration dates of the Company’s outstanding interest rate swap agreements were as follows:

September 30, 2025

Notional Amount
Currency

Notional Amount
(in millions)

Fixed
Rate

Effective
Date

Expiration
Date

USD

400.0

1.283%

February 2023

March 2028

September 30, 2024

Notional Amount
Currency

Notional Amount
(in millions)

Fixed
Rate

Effective
Date

Expiration
Date

USD

400.0

1.283%

February 2023

March 2028

Schedule of Financial Assets and Liabilities Recorded at Fair Value on a Recurring Basis

Below are the Company’s non-pension financial assets and liabilities recorded at fair value on a recurring basis within the ASC 820-10 fair value hierarchy:


	As of September 30, 2025
	Balance Sheet Location	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Total Fair Value

	(in millions)
Interest rate contracts	Other current assets	$	—	$	9.0	$	—	$	9.0
Interest rate contracts	Other non-current assets	—		10.0		—		10.0
Interest rate contracts	Other current liabilities	—		(1.8)		—		(1.8)
Interest rate contracts	Other long-term liabilities	—		(2.8)		—		(2.8)
Credit facility investment	Other non-current assets	—		—		17.4		17.4
Contingent Consideration	Other long-term liabilities	—		(7.5)		—		(7.5)
Equity investment	Other non-current assets	21.9		—		—		21.9
Total net assets at fair value		$	21.9	$	6.9	$	17.4	$	46.2


	As of September 30, 2024
	Balance Sheet Location	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Total Fair Value

	(in millions)
Interest rate contracts	Other current assets	$	—	$	9.2	$	—	$	9.2
Interest rate contracts	Other non-current assets	—		16.5		—		16.5
Interest rate contracts	Other current liabilities	—		(0.9)		—		(0.9)
Interest rate contracts	Other long-term liabilities	—		(3.6)		—		(3.6)
Credit facility investment	Other non-current assets	—		—		21.9		21.9
Equity investment	Other non-current assets	19.4		—		—		19.4
Total net assets at fair value		$	19.4	$	21.2	$	21.9	$	62.5

Schedule of Changes in Fair Value of Level 3 Investment Assets

The table below sets forth a summary of changes in the fair value of the Company’s Level 3 investment assets:


	Year-ended September 30, 2025
	Beginning Balance		Investment Gains/(Losses)	Interest Earned	Loans	Collections	Ending Balance

	(in millions)
Credit facility investment including accrued interest	$	21.9	0.1	1.1	19.0	(24.7)	$	17.4


	Year-ended September 30, 2024
	Beginning Balance		Investment Gains/(Losses)	Interest Earned	Loans	Collections	Ending Balance
	(in millions)
Credit facility investment including accrued interest	$	—	0.5	0.5	32.5	(11.6)	$	21.9

- Definition

Tabular disclosure of the fair value measurement of assets using significant unobservable inputs (Level 3), a reconciliation of the beginning and ending balances, separately presenting changes during the period attributable to the following: (1) total gains or losses for the period (realized and unrealized), segregating those gains or losses included in earnings (or changes in net assets) and gains or losses recognized in other comprehensive income (loss), and a description of where those gains or losses included in earnings (or changes in net assets) are reported in the statement of income (or activities); (2) purchases, sales, issues, and settlements (each type disclosed separately); and (3) transfers in and transfers out of Level 3 (for example, transfers due to changes in the observability of significant inputs), by class of asset.

+ References + Details

Debt - Schedule of Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Sep. 30, 2024
Debt Instrument [Line Items]
Total debt	$ 2,743,700	$ 2,539,800
Less: Current portion of debt and short-term borrowings	(66,300)	(66,900)
Less: Unamortized debt issuance costs	(30,200)	(22,600)
Long-term debt	2,647,220	2,450,330
Credit Agreement
Debt Instrument [Line Items]
Total debt	1,439,900	1,446,600
2027 Senior Notes
Debt Instrument [Line Items]
Total debt	0	997,300
2033 Senior Notes
Debt Instrument [Line Items]
Total debt	1,200,000	0
Other debt
Debt Instrument [Line Items]
Total debt	$ 103,800	$ 95,900

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

Reclassifications out of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ 2,370,410	$ 2,383,711	$ 2,605,379
Other comprehensive income (loss) before reclassification	(2,400)	56,000	59,400
Amounts reclassified from accumulated other comprehensive loss	(7,900)	(12,100)	(6,300)
Ending balance	2,696,184	2,370,410	2,383,711
Accumulated Other Comprehensive Loss
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(882,671)	(926,577)	(979,675)
Ending balance	(893,027)	(882,671)	(926,577)
Pension Related Adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(252,000)	(226,000)	(217,300)
Other comprehensive income (loss) before reclassification	(1,300)	(26,600)	(10,900)
Amounts reclassified from accumulated other comprehensive loss	1,900	600	2,200
Ending balance	(251,400)	(252,000)	(226,000)
Foreign Currency Translation Adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(646,500)	(739,700)	(799,300)
Other comprehensive income (loss) before reclassification	(5,900)	93,200	59,600
Amounts reclassified from accumulated other comprehensive loss	0	0	0
Ending balance	(652,400)	(646,500)	(739,700)
Loss on Derivative Instruments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	15,800	39,100	36,900
Other comprehensive income (loss) before reclassification	4,800	(10,600)	10,700
Amounts reclassified from accumulated other comprehensive loss	(9,800)	(12,700)	(8,500)
Ending balance	$ 10,800	$ 15,800	$ 39,100

- Definition

Amount after tax, before reclassification adjustments of other comprehensive income (loss).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14A
-Publisher FASB
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
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-URI https://asc.fasb.org/1943274/2147482765/220-10-50-5

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://fasb.org/us-gaap/role/ref/legacyRef
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482739/220-10-55-15

+ Details

- Definition

Amount after tax of reclassification adjustments of other comprehensive income (loss).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
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+ Details

- Definition

Amount of equity (deficit) attributable to parent and noncontrolling interest. Excludes temporary equity.

+ References

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+ Details

Joint Ventures and Variable Interest Entities - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2023	Jun. 30, 2023	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Joint Ventures and Variable Interest Entities [Line Items]
Total revenue of consolidated joint ventures			$ 16,139,622	$ 16,105,498	$ 14,378,461
Impairment loss	$ 35,900	$ 307,000
Consolidated Joint Ventures
Joint Ventures and Variable Interest Entities [Line Items]
Total revenue of consolidated joint ventures			$ 1,698,400	$ 2,242,800	$ 1,984,300

- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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+ Details

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References + Details

Debt - Credit Agreement (Details) - USD ($)	Apr. 19, 2024	Sep. 30, 2025	Sep. 30, 2024
Credit Agreement \| Maximum
Debt Instrument [Line Items]
Consolidated leverage ratio	4.00
New Revolving Credit Facility \| Other Currency
Debt Instrument [Line Items]
Interest rate, basis spread (as percent)	1.225%
New Revolving Credit Facility \| Base Rate \| USD
Debt Instrument [Line Items]
Debt instrument, floor rate (as percent)	0.00%
Interest rate, basis spread (as percent)	0.225%
New Revolving Credit Facility \| SOFR \| USD
Debt Instrument [Line Items]
Debt instrument, floor rate (as percent)	0.00%
Debt instrument, spread adjustment rate (as percent)	0.10%
Interest rate, basis spread (as percent)	1.225%
New Revolving Credit Facility \| Credit Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 1,500,000,000
New Term Loan A Facility \| Credit Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 750,000,000
New Term Loan B Facility \| Base Rate
Debt Instrument [Line Items]
Debt instrument, floor rate (as percent)	0.00%
Interest rate, basis spread (as percent)	0.75%
New Term Loan B Facility \| SOFR
Debt Instrument [Line Items]
Debt instrument, floor rate (as percent)	0.00%
Debt instrument, spread adjustment rate (as percent)	0.00%
Interest rate, basis spread (as percent)	1.75%
New Term Loan B Facility \| Credit Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 700,000,000
Revolving Credit Facility \| Credit Agreement
Debt Instrument [Line Items]
Outstanding standby letters of credit		$ 4,400,000	$ 4,400,000
Current borrowing capacity		$ 1,495,600,000	$ 1,495,600,000

Other Financial Information - Schedule of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Sep. 30, 2024
Other Financial Information [Abstract]
Accrued salaries and benefits	$ 727,000	$ 620,400
Accrued contract costs	1,419,000	1,354,700
Other accrued expenses	344,500	410,600
Total	$ 2,490,480	$ 2,385,731

Discontinued Operations, Goodwill and Intangible Assets - Schedule of Significant Components Included in Statement of Cash Flows for Discontinued Operations (Details) - Held for Sale - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Discontinued Operations, Goodwill and Intangible Assets
Payments for capital expenditures	$ 0.0	$ (2.5)	$ (6.2)
Noncash increase in noncurrent assets held for sale due to deconsolidation of a joint venture	41.6	0.0	0.0
Noncash decrease in noncontrolling interest due to deconsolidation of a joint venture	$ (13.8)	$ 0.0	$ 0.0

Significant Accounting Policies (Policies)	12 Months Ended
Significant Accounting Policies (Policies)	Sep. 30, 2025
Accounting Policies [Abstract]
Fiscal Year	Fiscal Year—The Company reports its annual results of operations based on 52-or 53- week periods ending on the Friday nearest September 30. Certain prior period amounts in the consolidated financial statements and accompanying notes have been reclassified to conform with the current period’s presentation.
Use of Estimates	Use of Estimates—The preparation of financial statements in conformity with accounting principles generally accepted in the United States (GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. The more significant estimates affecting amounts reported in the consolidated financial statements relate to revenues under long-term contracts and self-insurance accruals. Actual results could differ from those estimates.
Principles of Consolidation	Principles of Consolidation and Presentation—The consolidated financial statements include the accounts of all majority-owned subsidiaries and joint ventures in which the Company is the primary beneficiary. All inter-company accounts have been eliminated in consolidation. Also see Note 6 regarding joint ventures and variable interest entities.
Presentation	Principles of Consolidation and Presentation—The consolidated financial statements include the accounts of all majority-owned subsidiaries and joint ventures in which the Company is the primary beneficiary. All inter-company accounts have been eliminated in consolidation. Also see Note 6 regarding joint ventures and variable interest entities.
Government Contract Matters	Government Contract Matters—The Company’s federal government and certain state and local agency contracts are subject to, among other regulations, regulations issued under the Federal Acquisition Regulations (FAR). These regulations can limit the recovery of certain specified indirect costs on contracts and subjects the Company to ongoing multiple audits by government agencies such as the Defense Contract Audit Agency (DCAA). In addition, most of the Company’s federal and state and local contracts are subject to termination at the discretion of the client. Audits by the DCAA and other agencies consist of reviews of the Company’s overhead rates, operating systems and cost proposals to ensure that the Company accounted for such costs in accordance with the Cost Accounting Standards of the FAR (CAS). If the DCAA determines the Company has not accounted for such costs consistent with CAS, the DCAA may disallow these costs. There can be no assurance that audits by the DCAA or other governmental agencies will not result in material cost disallowances in the future.
Cash and Cash Equivalents	Cash and Cash Equivalents—The Company’s cash equivalents include highly liquid investments which have an initial maturity of three months or less.
Allowance for Doubtful Accounts	Allowance for Doubtful Accounts—The Company records its accounts receivable net of an allowance for doubtful accounts. This allowance for doubtful accounts is estimated based on management’s evaluation of the contracts involved and the financial condition of its clients. The factors the Company considers in its contract evaluations include, but are not limited to: •Client type—federal or state and local government or commercial client; •Historical contract performance; •Historical collection and delinquency trends; •Client credit worthiness; and •General economic conditions.
Derivative Financial Instruments	Derivative Financial Instruments—The Company accounts for its derivative instruments as either assets or liabilities and carries them at fair value. For derivative instruments that hedge the exposure to variability in expected future cash flows that are designated as cash flow hedges, the effective portion of the gain or loss on the derivative instrument is reported as a component of accumulated other comprehensive income in stockholders’ equity and reclassified into income in the same period or periods during which the hedged transaction affects earnings. The ineffective portion of the gain or loss on the derivative instrument, if any, is recognized in current income. To receive hedge accounting treatment, cash flow hedges must be highly effective in offsetting changes to expected future cash flows on hedged transactions. The net gain or loss on the effective portion of a derivative instrument that is designated as an economic hedge of the foreign currency translation exposure generated by the re-measurement of certain assets and liabilities denominated in a non-functional currency in a foreign operation is reported in the same manner as a foreign currency translation adjustment. Accordingly, any gains or losses related to these derivative instruments are recognized in current income. Derivatives that do not qualify as hedges are adjusted to fair value through current income.
Fair Value of Financial Instruments	Fair Value of Financial Instruments—The Company determines the fair values of its financial instruments, including short-term investments, debt instruments and derivative instruments, and pension and post-retirement plan assets based on inputs or assumptions that market participants would use in pricing an asset or a liability. The Company categorizes its instruments using a valuation hierarchy for disclosure of the inputs used to measure fair value. This hierarchy prioritizes the inputs into three broad levels as follows: Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities; Level 2 inputs are quoted prices for similar assets and liabilities in active markets or inputs that are observable for the asset or liability, either directly or indirectly through market corroboration, for substantially the full term of the financial instrument; Level 3 inputs are unobservable inputs based on the Company’s assumptions used to measure assets and liabilities at fair value. The classification of a financial asset or liability within the hierarchy is determined based on the lowest level input that is significant to the fair value measurement. The carrying amounts of cash and cash equivalents, accounts receivable and accounts payable approximate fair value because of the short maturities of these instruments. The carrying amount of the revolving credit facility approximates fair value because the interest rates are based upon variable reference rates. The Company’s fair value measurement methods may produce a fair value calculation that may not be indicative of net realizable value or reflective of future fair values. Although the Company believes its valuation methods are appropriate and consistent with those used by other market participants, the use of different methodologies or assumptions to determine fair value could result in a different fair value measurement at the reporting date.
Property and Equipment	Property and Equipment—Property and equipment are recorded at cost and are depreciated over their estimated useful lives using the straight-line method. Expenditures for maintenance and repairs are expensed as incurred. Typically, estimated useful lives range from ten to forty-five years for buildings, three to ten years for furniture and fixtures and three to twelve years for computer systems and equipment. Leasehold improvements are amortized on a straight-line basis over the shorter of their estimated useful lives or the remaining terms of the underlying lease agreement.
Long-Lived Assets	Long-Lived Assets—Long-lived assets to be held and used are reviewed for impairment whenever events or circumstances indicate that the assets may not be recoverable. The carrying amount of an asset to be held and used is not recoverable if it exceeds the sum of the undiscounted cash flows expected from the use and eventual disposition of the asset. For assets to be held and used, impairment losses are recognized based upon the excess of the asset’s carrying amount over the fair value of the asset. For long-lived assets to be disposed, impairment losses are recognized at the lower of the carrying amount or fair value less cost to sell.
Goodwill and Acquired Intangible Assets	Goodwill and Acquired Intangible Assets—Goodwill represents the excess of amounts paid over the fair value of net assets acquired from an acquisition. In order to determine the amount of goodwill resulting from an acquisition, the Company performs an assessment to determine the value of the acquired company’s tangible and identifiable intangible assets and liabilities. In its assessment, the Company determines whether identifiable intangible assets exist, which typically include backlog, customer relationships and intellectual property. Intangible assets are amortized over the period in which the contractual or economic benefits of the intangible assets are expected to be realized. The Company tests goodwill for impairment annually for each reporting unit in the fourth quarter of the fiscal year and between annual tests, if events occur or circumstances change which suggest that goodwill should be evaluated. Such events or circumstances include significant changes in legal factors and business climate, recent losses at a reporting unit, and industry trends, among other factors. A reporting unit is defined as an operating segment or one level below an operating segment. The Company’s impairment tests are performed at the operating segment level as they represent the Company’s reporting units. Goodwill is evaluated for impairment either by assessing qualitative factors or by performing a quantitative assessment. Qualitative factors, such as overall financial performance, industry or market considerations, or other relevant events, are assessed to determine if it is more likely than not that the fair value of the reporting units is less than their carrying amounts. During a quantitative impairment test, the Company estimates the fair value of the reporting unit using income and market approaches, and compares that amount to the carrying value of that reporting unit. In the event the fair value of the reporting unit is determined to be less than the carrying value, goodwill is impaired, and an impairment loss is recognized equal to the excess, limited to the total amount of goodwill allocated to the reporting unit. The impairment evaluation process includes, among other things, making assumptions about variable such as revenue growth rates, profitability, discount rates, and industry market multiples, which are subject to a high degree of judgment. See also Note 3.
Pension Plans	Pension Plans—The Company has certain defined benefit pension plans. The Company calculates the market-related value of assets, which is used to determine the return-on-assets component of annual pension expense and the cumulative net unrecognized gain or loss subject to amortization. This calculation reflects the Company’s anticipated long-term rate of return and amortization of the difference between the actual return (including capital, dividends, and interest) and the expected return over a five-year period. Cumulative net unrecognized gains or losses that exceed 10% of the greater of the projected benefit obligation or the fair market related value of plan assets are subject to amortization.
Insurance Reserves	Insurance Reserves—The Company maintains insurance for certain insurable business risks. Insurance coverage contains various retention and deductible amounts for which the Company accrues a liability based upon reported claims and an actuarially determined estimated liability for certain claims incurred but not reported. It is generally the Company’s policy not to accrue for any potential legal expense to be incurred in defending the Company’s position. The Company believes that its accruals for estimated liabilities associated with professional and other liabilities are sufficient and any excess liability beyond the accrual is not expected to have a material adverse effect on the Company’s results of operations or financial position.
Foreign Currency Translation	Foreign Currency Translation—The Company’s functional currency is generally the U.S. dollar, except for foreign operations where the functional currency is generally the local currency. Results of operations for foreign entities are translated to U.S. dollars using the average exchange rates during the period. Assets and liabilities for foreign entities are translated using the exchange rates in effect as of the date of the balance sheet. Resulting translation adjustments are recorded as a foreign currency translation adjustment into other accumulated comprehensive income/(loss) in stockholders’ equity. The Company uses foreign currency forward contracts from time to time to mitigate foreign currency risk. The Company limits exposure to foreign currency fluctuations in most of its contracts through provisions that require client payments in currencies corresponding to the currency in which costs are incurred. As a result of this natural hedge, the Company generally does not need to hedge foreign currency cash flows for contract work performed.
Noncontrolling Interests	Noncontrolling Interests—Noncontrolling interests represent the equity investments of the minority owners in the Company’s joint ventures and other subsidiary entities that the Company consolidates in its financial statements.
Income Taxes	Income Taxes—The Company files a consolidated U.S. federal corporate income tax return and combined / consolidated state tax returns and separate company state tax returns. The Company accounts for certain income and expense items differently for financial reporting and income tax purposes. Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax basis of assets and liabilities, applying enacted statutory tax rates in effect for the year in which the differences are expected to reverse. In determining the need for a valuation allowance, management reviews both positive and negative evidence, including the nature, frequency, and severity of cumulative financial reporting losses in recent years, the future reversal of existing temporary differences, predictability of future taxable income exclusive of reversing temporary differences of the character necessary to realize the asset, relevant carryforward periods, taxable income in carry-back years if carry-back is permitted under tax law, and prudent and feasible tax planning strategies that would be implemented, if necessary, to protect against the loss of the deferred tax asset that would otherwise expire. Based upon management’s assessment of all available evidence, the Company has concluded that it is more likely than not that the deferred tax assets, net of valuation allowance, will be realized. On December 22, 2017, the United States enacted the Tax Cuts and Jobs Act, which significantly changed U.S. tax law and included a provision to tax global intangible low-taxed income (GILTI) of foreign subsidiaries. The Company recognizes taxes due under the GILTI provision as a current period expense. On July 4, 2025, the U.S. government enacted the One Big Beautiful Bill Act which permanently extends many provisions of the Tax Cuts and Jobs Act of 2017 and introduces new tax provisions relevant for multinational businesses. Most of the new provisions take effect starting in fiscal 2026. Based on its assessment, the Company does not expect the legislation to have a material impact on its consolidated financial statements.
New Accounting Pronouncements and Changes in Accounting	In November 2023, the Financial Accounting Standards Board (FASB) amended the guidance of Accounting Standards Codification (ASC) 280, Segment Reporting, requiring public entities to disclose significant segment expenses and other segment items on an interim basis. The new guidance is effective for the Company for its annual financial statements in fiscal year 2025 and for its interim financial statements in fiscal year 2026. The adoption of the new guidance did not significantly impact the Company's financial presentation. In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, which includes amendments that further enhance the income tax information through improvements to income tax disclosures primarily related to the rate reconciliation and income taxes paid. The update also includes certain other amendments to improve the effectiveness of income tax disclosures. The amendments are effective for the Company’s annual periods beginning October 1, 2025, with early adoption permitted. The Company is currently evaluating the impact that the adoption of this new guidance will have on its financial statement presentation. In November 2024, the FASB issued ASU 2024-03 requiring public entities to provide disaggregated disclosures in the notes of the financial statements of certain categories of expenses that are included in expense line items on the face of the income statement on an interim basis. The new guidance is effective for the Company for its annual financial statements in fiscal year 2027 and for its interim financial statements in fiscal year 2028, with early adoption permitted. The Company is currently evaluating the impact that the adoption of this new guidance will have on its financial statements. In September 2025, the FASB issued ASU 2025-06 to clarify and modernize the accounting for costs related to internal-use software. The guidance removes references to project stages used in ASC 350-40 and clarifies the threshold entities should apply to begin capitalizing internal-use software costs. The new guidance is effective for the Company starting October 1, 2028, and the Company may apply the guidance using a prospective, retrospective, or modified transition approach. The Company is currently evaluating the impact that the adoption of this new guidance will have on its financial statements.

Leases - Schedule of Components of Lease Expenses (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Leases [Abstract]
Operating lease cost	$ 147.4	$ 149.1	$ 164.0
Finance lease cost:
Amortization of right-of-use assets	33.9	28.4	23.1
Interest on lease liabilities	3.7	2.9	2.6
Variable lease cost	32.0	34.6	34.1
Total lease cost	$ 217.0	$ 215.0	$ 223.8

Pension Benefit Obligations (Tables)

12 Months Ended

Sep. 30, 2025

Retirement Benefits [Abstract]

Schedule of Reconciliations of Changes In the U.S. and International Plans' Benefit Obligations


	Fiscal Year Ended
	September 30, 2025				September 30, 2024				September 30, 2023
	U.S.		Int’l		U.S.		Int’l		U.S.		Int’l

	(in millions)
Change in benefit obligation:
Benefit obligation at beginning of year	$	186.9	$	860.4	$	181.2	$	756.2	$	198.1	$	791.2
Service cost	—		0.2		—		0.2		—		0.3
Participant contributions	0.1		0.2		0.1		0.3		0.1		0.2
Interest cost	7.9		40.1		9.7		43.7		9.8		47.7
Benefits and expenses paid	(17.1)		(46.2)		(17.6)		(47.7)		(17.2)		(42.2)
Actuarial loss (gain)	(0.2)		(69.8)		13.5		37.0		(8.8)		(112.5)
Plan settlements	(0.7)		—		—		(3.2)		(1.5)		(1.5)
Transfers in	—		—		—		—		0.7		—
Foreign currency translation loss	—		4.4		—		73.9		—		73.0
Benefit obligation at end of year	$	176.9	$	789.3	$	186.9	$	860.4	$	181.2	$	756.2

Schedule of Reconciliations of Changes In Fair Value of Assets


	Fiscal Year Ended
	September 30, 2025				September 30, 2024				September 30, 2023
	U.S.		Int’l		U.S.		Int’l		U.S.		Int’l

	(in millions)
Change in plan assets
Fair value of plan assets at beginning of year	$	109.0	$	804.3	$	98.8	$	673.3	$	101.4	$	683.5
Actual return on plan assets	3.0		(15.1)		15.8		89.0		7.8		(54.2)
Employer contributions	10.6		23.7		11.9		25.1		8.2		24.8
Participant contributions	0.1		0.2		0.1		0.3		0.1		0.2
Benefits and expenses paid	(17.1)		(46.2)		(17.6)		(47.7)		(17.2)		(42.2)
Plan settlements	(0.7)		—		—		(3.2)		(1.5)		(1.5)
Foreign currency translation gain	—		5.0		—		67.5		—		62.7
Fair value of plan assets at end of year	$	104.9	$	771.9	$	109.0	$	804.3	$	98.8	$	673.3

Schedule of Reconciliations of Funded Status


	Fiscal Year Ended
	September 30, 2025				September 30, 2024				September 30, 2023
	U.S.		Int’l		U.S.		Int’l		U.S.		Int’l

	(in millions)
Reconciliation of funded status:
Funded status at end of year	$	(72.0)	$	(17.4)	$	(77.9)	$	(56.1)	$	(82.4)	$	(82.9)
Contribution made after measurement date	N/A		N/A		N/A		N/A		N/A		N/A
Net amount recognized at end of year	$	(72.0)	$	(17.4)	$	(77.9)	$	(56.1)	$	(82.4)	$	(82.9)

Schedule of Amounts Recognized In the Consolidated Balance Sheets

The following table sets forth the amounts recognized in the consolidated balance sheets as of September 30, 2025, 2024 and 2023:


	Fiscal Year Ended
	September 30, 2025				September 30, 2024				September 30, 2023
	U.S.		Int’l		U.S.		Int’l		U.S.		Int’l

	(in millions)
Amounts recognized in the consolidated balance sheets:
Other non-current assets	$	—	$	52.3	$	—	$	46.6	$	—	$	38.7
Accrued expenses and other current liabilities	(8.5)		—		(8.3)		—		(8.4)		—
Pension benefit obligations	(63.5)		(69.7)		(69.6)		(102.7)		(74.0)		(121.6)
Net amount recognized in the balance sheet	$	(72.0)	$	(17.4)	$	(77.9)	$	(56.1)	$	(82.4)	$	(82.9)

Schedule of Reconciliation of Amounts In the Consolidated Statements of Stockholder's Equity

The following table details the reconciliation of amounts in the consolidated statements of stockholders’ equity for the fiscal years ended September 30, 2025, 2024 and 2023:


	Fiscal Year Ended
	September 30, 2025				September 30, 2024				September 30, 2023
	U.S.		Int’l		U.S.		Int’l		U.S.		Int’l

	(in millions)
Reconciliation of amounts in consolidated statements of stockholders’ equity:
Prior service cost	$	(0.1)	$	(1.2)	$	(0.1)	$	(1.3)	$	(0.1)	$	(1.2)
Net loss	(75.4)		(235.5)		(77.6)		(234.9)		(77.5)		(207.1)
Total recognized in accumulated other comprehensive loss	$	(75.5)	$	(236.7)	$	(77.7)	$	(236.2)	$	(77.6)	$	(208.3)

Schedule of Components of Net Periodic Cost

The following table details the components of net periodic benefit cost for the Company’s pension plans for fiscal years ended September 30, 2025, 2024 and 2023:


	Fiscal Year Ended
	September 30, 2025				September 30, 2024				September 30, 2023
	U.S.		Int’l		U.S.		Int’l		U.S.		Int’l

	(in millions)
Components of net periodic benefit cost:
Service costs	$	—	$	0.2	$	—	$	0.2	$	—	$	0.3
Interest cost on projected benefit obligation	7.9		40.1		9.7		43.7		9.8		47.7
Expected return on plan assets	(4.8)		(52.2)		(5.5)		(57.4)		(5.8)		(60.8)
Amortization of prior service costs	—		0.1		—		0.1		—		0.1
Amortization of net loss (gain)	3.7		(1.3)		3.1		(2.3)		3.5		(0.6)
Settlement loss (gain) recognized	0.1		—		—		0.1		(0.1)		0.2
Net periodic benefit cost (credit)	$	6.9	$	(13.1)	$	7.3	$	(15.6)	$	7.4	$	(13.1)

Schedule of Amounts Included In Accumulated Other Comprehensive Loss Expected to Be Recognized as Components of Net Periodic Benefit Cost

Amounts included in accumulated other comprehensive loss as of September 30, 2025 that are expected to be recognized as components of net periodic benefit cost during fiscal 2026 are (in millions):


	U.S.		Int’l
Amortization of prior service cost	$	—	$	(0.1)
Amortization of net actuarial (losses) gain	(3.8)		0.6
Total	$	(3.8)	$	0.5

Schedule of Additional Year-End Information for Pension Plans With Accumulated Benefit Obligations In Excess of Plan Assets

The table below provides additional year-end information for pension plans with accumulated benefit obligations in excess of plan assets.


	Fiscal Year Ended
	September 30, 2025				September 30, 2024				September 30, 2023
	U.S.		Int’l		U.S.		Int’l		U.S.		Int’l

	(in millions)
Projected benefit obligation	$	165.8	$	395.6	$	175.1	$	649.8	$	168.8	$	628.1
Accumulated benefit obligation	$	165.8	$	395.6	$	175.1	$	649.8	$	168.8	$	628.1
Fair value of plan assets	$	104.9	$	325.9	$	109.0	$	547.1	$	98.8	$	506.5

Schedule of Expected Future Benefit Payments

The table below provides the expected future benefit payments, in millions:


Year Ending September 30,	U.S.		Int’l
2026	$	26.8	$	52.2
2027	18.3		51.3
2028	17.6		52.9
2029	16.6		54.8
2030	15.7		56.0
2031-2035	66.0		297.5
Total	$	161.0	$	564.7

Schedule of Underlying Assumptions for Pension Plans

The underlying assumptions for the pension plans are as follows:


	Fiscal Year Ended
	September 30, 2025				September 30, 2024				September 30, 2023
	U.S.		Int’l		U.S.		Int’l		U.S.		Int’l

	(in millions)
Weighted-average assumptions to determine benefit obligation:
Discount rate	5.01	%	5.83	%	4.73	%	5.04	%	5.76	%	5.65	%
Salary increase rate	N/A		2.81	%	N/A		2.91	%	N/A		3.06	%
Weighted-average assumptions to determine net periodic benefit cost:
Discount rate	4.73	%	5.04	%	5.76	%	5.65	%	5.40	%	5.27	%
Salary increase rate	N/A		2.91	%	N/A		3.06	%	N/A		3.48	%
Expected long-term rate of return on plan assets	6.25	%	5.51	%	6.90	%	5.74	%	7.00	%	6.04	%

Schedule of Target Allocation and Pension Plan Asset Allocation and Fair Values of Pension Plan Assets By Major Asset Categories

The following table summarizes the Company’s target allocation for 2025 and pension plan asset allocation, both U.S. and International, as of September 30, 2025 and 2024:


					Percentage of Plan Assets as of September 30,
	Target Allocations				2025				2024
	U.S.		Int’l		U.S.		Int’l		U.S.		Int’l
Asset Category:
Equities	18	%	25	%	19	%	24	%	24	%	25	%
Debt	78		65		74		64		67		64
Cash	—		3		2		2		4		2
Diversified and other	4		7		5		10		5		9
Total	100	%	100	%	100	%	100	%	100	%	100	%

As of September 30, 2025, the fair values of the Company’s pension plan assets by major asset categories were as follows:


			Fair Value Measurement as of September 30, 2025
	Total Carrying Value as of September 30, 2025		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Investments measured at NAV

	(in millions)
Cash and cash equivalents	$	20.5	$	20.5	$	—	$	—	$	—
Debt securities	361.4		361.4		—		—		—
Investment funds:
Diversified and equity funds	272.5		71.5		14.1		—		186.9
Fixed income funds	220.5		22.7		4.4		—		193.4
Absolute return fund	5.1		—		—		—		5.1
Derivative instruments and other	(3.2)		9.9		(13.1)		—		—
Total	$	876.8	$	486.0	$	5.4	$	—	$	385.4

As of September 30, 2024, the fair values of the Company’s pension plan assets by major asset categories were as follows:


			Fair Value Measurement as of September 30, 2024
	Total Carrying Value as of September 30, 2024		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Investments measured at NAV

	(in millions)
Cash and cash equivalents	$	22.1	$	22.1	$	—	$	—	$	—
Debt securities	391.5		391.5		—		—		—
Investment funds:
Diversified and equity funds	286.7		48.5		13.5		—		224.7
Fixed income funds	213.9		17.3		4.1		—		192.5
Absolute return fund	5.9		—		—		—		5.9
Derivative instruments and other	(6.8)		8.2		(15.0)		—		—
Total	$	913.3	$	487.6	$	2.6	$	—	$	423.1

Schedule II: Valuation and Qualifying Accounts

12 Months Ended

Sep. 30, 2025

SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]

Schedule II: Valuation and Qualifying Accounts

(amounts in millions)


	Balance at Beginning of Year		Additions Charged to Cost of Revenue		Deductions(a)		Other and Foreign Exchange Impact		Balance at the End of the Year
Allowance for Doubtful Accounts
Fiscal Year 2025	$	87.9	$	18.3	$	(20.6)	$	(0.8)	$	84.8
Fiscal Year 2024	$	94.2	$	30.9	$	(38.7)	$	1.5	$	87.9
Fiscal Year 2023	$	104.0	$	40.9	$	(50.8)	$	0.1	$	94.2

_____________________________________________________________

(a)Primarily relates to accounts written-off and recoveries

Reportable Segments and Geographic Information - Schedule of Geographic Information (Details) - USD ($) $ in Millions	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Geographic Information
Total	$ 5,155.8	$ 4,558.9	$ 4,624.3
Americas
Geographic Information
Total	3,779.2	3,315.3	3,478.5
Europe, Middle East, India, Africa
Geographic Information
Total	1,025.5	872.9	803.5
Asia-Australia-Pacific
Geographic Information
Total	$ 351.1	$ 370.7	$ 342.3

Income Taxes - Schedule of Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Current:
Federal	$ 88,900	$ 15,100	$ 67,700
State	26,400	(78,600)	71,900
Foreign	56,100	63,500	52,800
Total current income tax expense	171,400	0	192,400
Deferred:
Federal	7,700	45,200	(71,800)
State	(6,500)	68,100	(84,300)
Foreign	31,400	39,600	19,800
Total deferred income tax expense (benefit)	32,600	152,900	(136,300)
Total income tax expense	$ 204,018	$ 152,900	$ 56,052

New Accounting Pronouncements and Changes in Accounting	12 Months Ended
New Accounting Pronouncements and Changes in Accounting	Sep. 30, 2025
Accounting Standards Update and Change in Accounting Principle [Abstract]
New Accounting Pronouncements and Changes in Accounting	New Accounting Pronouncements and Changes in Accounting In November 2023, the Financial Accounting Standards Board (FASB) amended the guidance of Accounting Standards Codification (ASC) 280, Segment Reporting, requiring public entities to disclose significant segment expenses and other segment items on an interim basis. The new guidance is effective for the Company for its annual financial statements in fiscal year 2025 and for its interim financial statements in fiscal year 2026. The adoption of the new guidance did not significantly impact the Company's financial presentation. In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, which includes amendments that further enhance the income tax information through improvements to income tax disclosures primarily related to the rate reconciliation and income taxes paid. The update also includes certain other amendments to improve the effectiveness of income tax disclosures. The amendments are effective for the Company’s annual periods beginning October 1, 2025, with early adoption permitted. The Company is currently evaluating the impact that the adoption of this new guidance will have on its financial statement presentation. In November 2024, the FASB issued ASU 2024-03 requiring public entities to provide disaggregated disclosures in the notes of the financial statements of certain categories of expenses that are included in expense line items on the face of the income statement on an interim basis. The new guidance is effective for the Company for its annual financial statements in fiscal year 2027 and for its interim financial statements in fiscal year 2028, with early adoption permitted. The Company is currently evaluating the impact that the adoption of this new guidance will have on its financial statements. In September 2025, the FASB issued ASU 2025-06 to clarify and modernize the accounting for costs related to internal-use software. The guidance removes references to project stages used in ASC 350-40 and clarifies the threshold entities should apply to begin capitalizing internal-use software costs. The new guidance is effective for the Company starting October 1, 2028, and the Company may apply the guidance using a prospective, retrospective, or modified transition approach. The Company is currently evaluating the impact that the adoption of this new guidance will have on its financial statements.

- Definition

The entire disclosure for change in accounting principle. Includes, but is not limited to, nature, reason, and method of adopting amendment to accounting standards or other change in accounting principle.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Derivative Financial Instruments and Fair Value Measurements - Schedule of Changes in Fair Value of Level 3 Investment Assets (Details) - Fair Value, Measurements, Recurring - Credit facility investment including accrued interest - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	$ 21.9	$ 0.0
Investment Gains/(Losses)	0.1	0.5
Interest Earned	1.1	0.5
Loans	19.0	32.5
Collections	(24.7)	(11.6)
Ending Balance	$ 17.4	$ 21.9

Derivative Financial Instruments and Fair Value Measurements - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023	Jun. 30, 2022	Sep. 30, 2021
Derivative [Line Items]
Gain recorded representing decrease in fair value	$ 2.5	$ 7.2
Interest Rate Swap \| Cash Flow Hedging \| Designated as Hedging Instrument
Derivative [Line Items]
Notional value					$ 400.0
Fixed interest rate (as percent)					1.283%
Material losses recognized in income	0.0	0.0	$ 0.0
Interest Rate Cap \| Cash Flow Hedging \| Designated as Hedging Instrument
Derivative [Line Items]
Notional value				$ 300.0
Fixed interest rate (as percent)				3.465%
Derivative, basis spread on variable rate (as percent)				3.465%
FY 2025 Fourth Quarter Acquisition
Derivative [Line Items]
Maximum value of contingent consideration issued	17.7
February 2023 \| United States of America, Dollars \| Interest Rate Swap \| Cash Flow Hedging \| Designated as Hedging Instrument
Derivative [Line Items]
Notional value	$ 400.0	$ 400.0
Fixed interest rate (as percent)	1.283%	1.283%

Cybersecurity Risk Management and Strategy Disclosure	12 Months Ended
Cybersecurity Risk Management and Strategy Disclosure	Sep. 30, 2025
Cybersecurity Risk Management, Strategy, and Governance [Line Items]
Cybersecurity Risk Management Processes for Assessing, Identifying, and Managing Threats [Text Block]	We maintain a cybersecurity program designed to assess, identify and manage risks from cybersecurity threats that may result in adverse effects on the confidentiality, integrity and availability of our information systems. Dedicated security and information governance and compliance professionals administer the program with oversight by our senior management team. We utilize a combination of technology controls, service providers, and processes to actively monitor and protect our network and systems. All employees are required to participate in a number of information security training and awareness programs on an annual basis, which include training on how to identify and report cyber risks and events. We engage industry cybersecurity experts to evaluate and review our cybersecurity programs. These external reviews include regular audits, threat assessments, vulnerability scans, simulated attacks and other advice regarding information security practices. We regularly conduct incident response exercises with key stakeholders. To manage risks associated with third-party service providers, we typically perform a cybersecurity assessment on new vendors before they are onboarded as a supplier. We conduct periodic reviews of these vendors to evaluate continued compliance with our policies and standards. We strive to ensure that our contracts with such vendors require them to maintain security controls in line with industry practices, applicable laws and our policies. We rely on vendors to notify us in a timely manner of significant cybersecurity incidents, by virtue of the documents governing their relationship with us or applicable law.
Cybersecurity Risk Management Processes Integrated [Flag]	true
Cybersecurity Risk Management Processes Integrated [Text Block]	We maintain a cybersecurity program designed to assess, identify and manage risks from cybersecurity threats that may result in adverse effects on the confidentiality, integrity and availability of our information systems. Dedicated security and information governance and compliance professionals administer the program with oversight by our senior management team. We utilize a combination of technology controls, service providers, and processes to actively monitor and protect our network and systems. All employees are required to participate in a number of information security training and awareness programs on an annual basis, which include training on how to identify and report cyber risks and events. We engage industry cybersecurity experts to evaluate and review our cybersecurity programs. These external reviews include regular audits, threat assessments, vulnerability scans, simulated attacks and other advice regarding information security practices. We regularly conduct incident response exercises with key stakeholders. To manage risks associated with third-party service providers, we typically perform a cybersecurity assessment on new vendors before they are onboarded as a supplier. We conduct periodic reviews of these vendors to evaluate continued compliance with our policies and standards. We strive to ensure that our contracts with such vendors require them to maintain security controls in line with industry practices, applicable laws and our policies. We rely on vendors to notify us in a timely manner of significant cybersecurity incidents, by virtue of the documents governing their relationship with us or applicable law.
Cybersecurity Risk Management Third Party Engaged [Flag]	true
Cybersecurity Risk Third Party Oversight and Identification Processes [Flag]	true
Cybersecurity Risk Materially Affected or Reasonably Likely to Materially Affect Registrant [Flag]	false
Cybersecurity Risk Board of Directors Oversight [Text Block]	Our Board of Directors (“Board”) receives regular updates from management and external consultants which may address a broad range of cybersecurity and IT topics, including trends, regulatory developments, data security policies and practices, cybersecurity incidents, and ongoing efforts to further strengthen our security posture. Our Board reviews key metrics related to cybersecurity on a quarterly basis, and is notified of applicable cybersecurity incidents if and when they occur. The Chief Information Security Officer (“CISO”) heads the cybersecurity program which includes personnel based in several of our global locations. Our CISO brings over 25 years of experience, which includes both consulting and practitioner roles, and maintains the following certifications: Certified Information System Security Professional (CISSP), Certified in Risk and Information Systems Control (CRISC), and Certified Information Security Manager (CISM). Our CISO reports to our Chief Information Officer, up to the Chief Technology Officer, who meets with our Board at least annually to discuss cybersecurity risk and related topics.
Cybersecurity Risk Board Committee or Subcommittee Responsible for Oversight [Text Block]	Our CISO’s team is responsible for leading enterprise-wide cybersecurity strategy, policy, standards and processes. The CISO receives ongoing updates from his team regarding the prevention, detection, mitigation, and remediation of cybersecurity incidents.
Cybersecurity Risk Process for Informing Board Committee or Subcommittee Responsible for Oversight [Text Block]	Our Board reviews key metrics related to cybersecurity on a quarterly basis, and is notified of applicable cybersecurity incidents if and when they occur. Our CISO reports to our Chief Information Officer, up to the Chief Technology Officer, who meets with our Board at least annually to discuss cybersecurity risk and related topics.
Cybersecurity Risk Role of Management [Text Block]	Our CISO’s team is responsible for leading enterprise-wide cybersecurity strategy, policy, standards and processes. The CISO receives ongoing updates from his team regarding the prevention, detection, mitigation, and remediation of cybersecurity incidents. In the event of a cybersecurity incident, we have a plan which sets forth a framework to report such incidents to our cybersecurity incident response team. This framework is designed with the goal of enabling the response team to take actions to monitor, mitigate and remediate such incidents in a timely manner. As part of this incident response plan, we have retainers in place with professional service firms to assist with cybersecurity incidents if needed.
Cybersecurity Risk Management Positions or Committees Responsible [Flag]	true
Cybersecurity Risk Management Positions or Committees Responsible [Text Block]	The Chief Information Security Officer (“CISO”) heads the cybersecurity program which includes personnel based in several of our global locations. Our CISO brings over 25 years of experience, which includes both consulting and practitioner roles, and maintains the following certifications: Certified Information System Security Professional (CISSP), Certified in Risk and Information Systems Control (CRISC), and Certified Information Security Manager (CISM). Our CISO reports to our Chief Information Officer, up to the Chief Technology Officer, who meets with our Board at least annually to discuss cybersecurity risk and related topics. Our CISO’s team is responsible for leading enterprise-wide cybersecurity strategy, policy, standards and processes. The CISO receives ongoing updates from his team regarding the prevention, detection, mitigation, and remediation of cybersecurity incidents.
Cybersecurity Risk Management Expertise of Management Responsible [Text Block]	Our CISO brings over 25 years of experience, which includes both consulting and practitioner roles, and maintains the following certifications: Certified Information System Security Professional (CISSP), Certified in Risk and Information Systems Control (CRISC), and Certified Information Security Manager (CISM).
Cybersecurity Risk Process for Informing Management or Committees Responsible [Text Block]	Our CISO reports to our Chief Information Officer, up to the Chief Technology Officer, who meets with our Board at least annually to discuss cybersecurity risk and related topics.
Cybersecurity Risk Management Positions or Committees Responsible Report to Board [Flag]	true

Revenue Recognition - Schedule of Revenues Disaggregated by Revenue Sources (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Disaggregation of Revenue [Line Items]
Total revenue	$ 16,139,622	$ 16,105,498	$ 14,378,461
Americas
Disaggregation of Revenue [Line Items]
Total revenue	12,526,400	12,487,000	10,976,400
Europe, Middle East, India, Africa
Disaggregation of Revenue [Line Items]
Total revenue	2,153,300	2,141,500	1,937,300
Asia-Australia-Pacific
Disaggregation of Revenue [Line Items]
Total revenue	1,459,900	1,477,000	1,464,800
Cost reimbursable
Disaggregation of Revenue [Line Items]
Total revenue	6,196,100	6,361,400	6,128,800
Guaranteed maximum price
Disaggregation of Revenue [Line Items]
Total revenue	5,960,700	6,030,000	4,887,700
Fixed price
Disaggregation of Revenue [Line Items]
Total revenue	$ 3,982,800	$ 3,714,100	$ 3,362,000

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Income Statement [Abstract]
Revenue	$ 16,139,622	$ 16,105,498	$ 14,378,461
Cost of revenue	14,922,909	15,021,157	13,432,996
Gross profit	1,216,713	1,084,341	945,465
Equity in earnings of joint ventures	27,013	2,124	(279,352)
General and administrative expenses	(157,849)	(160,105)	(153,575)
Restructuring and acquisition costs	(59,355)	(98,918)	(188,404)
Income from operations	1,026,522	827,442	324,134
Other income	10,457	17,570	8,357
Interest income	62,894	58,560	40,251
Interest expense	(184,304)	(185,420)	(159,342)
Income from continuing operations before taxes	915,569	718,152	213,400
Income tax expense for continuing operations	204,018	152,900	56,052
Net income from continuing operations	711,551	565,252	157,348
Net loss from discontinued operations	(75,364)	(104,997)	(57,207)
Net income	636,187	460,255	100,141
Net income attributable to noncontrolling interests from continuing operations	(73,287)	(59,322)	(43,262)
Net income (loss) attributable to noncontrolling interests from discontinued operations	(1,126)	1,333	(1,547)
Net income attributable to noncontrolling interests	(74,413)	(57,989)	(44,809)
Net income attributable to AECOM from continuing operations	638,264	505,930	114,086
Net loss attributable to AECOM from discontinued operations	(76,490)	(103,664)	(58,754)
Net income attributable to AECOM	$ 561,774	$ 402,266	$ 55,332
Net income (loss) attributable to AECOM per share:
Basic continuing operations per share (in dollar per share)	$ 4.82	$ 3.73	$ 0.82
Basic discontinued operations per share (in dollar per share)	(0.58)	(0.76)	(0.42)
Basic earnings per share (in dollar per share)	4.24	2.97	0.40
Diluted continuing operations per share (in dollar per share)	4.79	3.71	0.81
Diluted discontinued operations per share (in dollar per share)	(0.58)	(0.76)	(0.42)
Diluted earnings per share (in dollar per share)	$ 4.21	$ 2.95	$ 0.39
Weighted average shares outstanding:
Basic (in shares)	132,373	135,544	138,614
Diluted (in shares)	133,311	136,453	140,109

Earnings Per Share

12 Months Ended

Sep. 30, 2025

Earnings Per Share [Abstract]

Earnings Per Share

Basic earnings per share (EPS) excludes dilution and is computed by dividing net income attributable to AECOM by the weighted average number of common shares outstanding for the period. Diluted EPS is computed by dividing net income attributable to AECOM by the weighted average number of common shares outstanding and potential common shares for the period. The Company includes as potential common shares the weighted average dilutive effects of equity awards using the treasury stock method. For the periods presented, equity awards excluded from the calculation of potential common shares were not significant.

The following table sets forth a reconciliation of the denominators of basic and diluted earnings per share:


	Fiscal Year Ended
	September 30, 2025	September 30, 2024	September 30, 2023

	(in millions)
Denominator for basic earnings per share	132.4	135.5	138.6
Potential common shares	0.9	1.0	1.5
Denominator for diluted earnings per share	133.3	136.5	140.1

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 636,187	$ 460,255	$ 100,141
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	175,917	178,812	175,725
Equity in (earnings) losses of unconsolidated joint ventures	(16,861)	1,276	282,291
Distribution of earnings from unconsolidated joint ventures	59,498	24,254	41,178
Non-cash stock compensation	61,439	61,520	45,882
Impairment of long-lived assets	0	0	86,199
Loss on sale of discontinued operations	0	90,412	43,222
Prepayment premium on redemption of unsecured senior notes	9,064	0	0
Foreign currency translation	2,316	15,468	969
Deferred income tax expense (benefit)	35,415	150,894	(135,878)
Other	916	(4,854)	6,388
Changes in operating assets and liabilities:
Accounts receivable and contract assets	334,419	(500,798)	(402,498)
Prepaid expenses and other assets	(82,707)	(207,359)	131,903
Accounts payable	(333,564)	391,176	169,514
Accrued expenses and other current liabilities	145,198	91,983	97,239
Contract liabilities	(210,549)	109,390	137,484
Other long-term liabilities	4,914	(34,939)	(83,779)
Net cash provided by operating activities	821,602	827,490	695,980
CASH FLOWS FROM INVESTING ACTIVITIES:
Payments for business acquisitions, net of cash acquired	(212,529)	(18,658)	0
Cash outflow from deconsolidation of a joint venture	(45,352)	0	0
Investment in unconsolidated joint ventures	(55,617)	(55,058)	(59,772)
Return of investment in unconsolidated joint ventures	30,995	0	20,874
Proceeds from sale of investments	0	3,180	5,977
Other investing activities	5,665	(21,000)	0
Proceeds from disposal of property and equipment	292	494	344
Payments for capital expenditures	(136,675)	(119,597)	(105,600)
Net cash used in by investing activities	(413,221)	(210,639)	(138,177)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from borrowings under credit agreements	2,212,924	6,169,266	3,506,668
Repayments of borrowings under credit agreements	(2,259,380)	(5,878,475)	(3,552,639)
Issuance of unsecured senior notes	1,188,600	0	0
Redemption of unsecured senior notes	(997,293)	0	0
Prepayment premium on redemption of unsecured senior notes	(9,064)	0	0
Cash paid for debt issuance costs	(3,889)	(16,573)	0
Dividends paid	(133,572)	(115,244)	(96,192)
Proceeds from issuance of common stock	40,084	34,556	32,897
Proceeds from exercise of stock options	2,056	2,056	6,168
Payments to repurchase common stock	(388,380)	(478,501)	(379,284)
Net distributions to noncontrolling interests	(53,380)	(16,177)	(2,223)
Other financing activities	(2,376)	3,632	11,670
Net cash used in financing activities	(403,670)	(295,460)	(472,935)
EFFECT OF EXCHANGE RATE CHANGES ON CASH	(3,834)	1,319	512
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	877	322,710	85,380
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR	1,584,862	1,262,152	1,176,772
CASH AND CASH EQUIVALENTS AT END OF YEAR	1,585,739	1,584,862	1,262,152
LESS: CASH AND CASH EQUIVALENTS INCLUDED IN CURRENT ASSETS HELD FOR SALE	0	(3,985)	(1,946)
CASH AND CASH EQUIVALENTS OF CONTINUING OPERATIONS AT END OF YEAR	1,585,739	1,580,877	1,260,206
SUPPLEMENTAL CASH FLOW INFORMATION:
Interest paid	(166,868)	(177,450)	(153,975)
Net income taxes paid	$ (91,968)	$ (139,972)	$ (78,448)

Other Financial Information - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended	12 Months Ended
	Nov. 18, 2025	Sep. 30, 2025	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Other Financials Information [Line Items]
Accrued contract costs including professional liability accruals		$ 1,419,000	$ 1,419,000	$ 1,354,700
Restructuring expenses incurred			59,355	98,918	$ 188,404
Accrued restructuring expenses		$ 15,000	15,000	11,900
Cash dividends declared (in dollars per share)		$ 0.26
Accrued and unpaid dividend		$ 37,600	37,600
Subsequent Event
Other Financials Information [Line Items]
Cash dividends declared (in dollars per share)	$ 0.31
Labor-Related Costs
Other Financials Information [Line Items]
Restructuring expenses incurred			32,000	18,700
Non-Labor Costs
Other Financials Information [Line Items]
Restructuring expenses incurred			27,300	80,200
Professional Liability Accrual
Other Financials Information [Line Items]
Accrued contract costs including professional liability accruals		$ 893,700	$ 893,700	$ 831,800

Share-Based Payments

12 Months Ended

Sep. 30, 2025

Share-Based Payment Arrangement [Abstract]

Share-Based Payments

Defined Contribution Plans—Substantially all permanent domestic employees are eligible to participate in defined contribution plans provided by the Company. Under these plans, participants may make contributions into a variety of funds, including a fund that is fully invested in Company stock. Employees are not required to allocate any funds to Company stock; however, the Company does provide an annual Company match in AECOM shares. Employees may generally reallocate their account balances on a daily basis; however, employees classified as insiders are restricted under the Company’s insider trading policy. Compensation expense for the employer contributions related to AECOM stock

issued under defined contribution plans during fiscal years ended September 30, 2025, 2024 and 2023 was $26.0 million, $24.7 million, and $23.1 million, respectively.

Stock Incentive Plans—Under the 2020 Stock Incentive Plan, the Company has up to 11.3 million securities remaining available for future issuance as of September 30, 2025. Stock options may be granted to employees and non-employee directors with an exercise price not less than the fair market value of the stock on the date of grant. Unexercised options expire seven years after date of grant.

The Company grants stock units to employees under its Performance Earnings Program (PEP), whereby units are earned and issued dependent upon meeting established cumulative performance objectives and vest over a three-year service period. Additionally, the Company issues restricted stock units to employees and directors which are earned based on service conditions. The grant date fair value of PEP awards and restricted stock unit awards is primarily based on that day’s closing market price of the Company’s common stock.

Restricted stock unit and PEP unit activity for the year ended September 30 was as follows:


	Restricted Stock Units	Weighted Average Grant-Date Fair Value		PEP Units	Weighted Average Grant-Date Fair Value

	(in millions)			(in millions)
Outstanding at September 30, 2022	1.0	$	53.05	0.7	$	60.60
Granted	0.3	$	83.64	0.2	$	94.64
PEP units earned (unearned)	—	$	—	0.2	$	43.19
Vested	(0.4)	$	44.35	(0.4)	$	43.19
Cancelled	(0.1)	$	62.09	—	$	71.71
Outstanding at September 30, 2023	0.8	$	68.34	0.7	$	75.54
Granted	0.3	$	92.30	0.2	$	104.66
PEP units earned (unearned)	—	$	—	0.2	$	52.50
Vested	(0.3)	$	50.14	(0.4)	$	52.50
Cancelled	0.0	$	77.32	—	$	89.76
Outstanding at September 30, 2024	0.8	$	83.96	0.7	$	95.38
Granted	0.2	$	110.65	0.2	$	129.28
PEP units earned (unearned)	—	$	—	0.1	$	85.46
Vested	(0.2)	$	75.72	(0.3)	$	85.46
Cancelled	(0.1)	$	95.85	(0.1)	$	109.53
Outstanding at September 30, 2025	0.7	$	95.64	0.6	$	109.74

Total compensation expense related to these share-based payments including stock options was $61.4 million, $61.5 million, and $45.9 million during the years ended September 30, 2025, 2024 and 2023, respectively. Unrecognized compensation expense related to total share-based payments outstanding as of September 30, 2025 and 2024 was $106.7 million and $68.7 million, respectively, to be recognized on a straight-line basis over the awards’ respective vesting periods which are generally three years.

Reportable Segments and Geographic Information - Schedule of Reconciles Total Segment Attributable Earnings Before Taxes and Amortization to Income From Continuing Operations Before Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Segment Reporting [Abstract]
Total segment attributable earnings before taxes and amortization	$ 1,181,300	$ 1,046,400	$ 642,400
Corporate general and administrative expenses	(148,900)	(145,100)	(141,000)
Restructuring and acquisition costs	(59,355)	(98,918)	(188,404)
Other income	(2,500)	2,100	(5,300)
Interest income	62,894	58,560	40,251
Interest expense	(184,304)	(185,420)	(159,342)
Amortization expense	(2,200)	(18,800)	(18,600)
Income attributable to noncontrolling interests from continuing operations	68,700	59,300	43,300
Income from continuing operations before taxes	$ 915,569	$ 718,152	$ 213,400

Joint Ventures and Variable Interest Entities - Schedule of Financial Information of Consolidated Joint Ventures (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Joint Ventures and Variable Interest Entities [Line Items]
Current assets	$ 6,730,227	$ 7,055,759
TOTAL ASSETS	12,200,249	12,061,669
Current liabilities	5,928,816	6,374,081
TOTAL LIABILITIES	9,504,065	9,691,259
Total AECOM deficit	2,492,584	2,184,205
Noncontrolling interests	203,600	186,205
TOTAL STOCKHOLDERS’ EQUITY	2,696,184	2,370,410	$ 2,383,711	$ 2,605,379
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	12,200,249	12,061,669
Consolidated Joint Ventures
Joint Ventures and Variable Interest Entities [Line Items]
Current assets	699,000	836,900
Non-current assets	84,400	83,100
TOTAL ASSETS	783,400	920,000
Current liabilities	591,400	763,600
Non-current liabilities	5,700	1,500
TOTAL LIABILITIES	597,100	765,100
Total AECOM deficit	(15,900)	(17,200)
Noncontrolling interests	202,200	172,100
TOTAL STOCKHOLDERS’ EQUITY	186,300	154,900
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$ 783,400	$ 920,000

Income Taxes - Schedule of Difference Between Federal Statutory Rate and the Effective Tax Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Rate Reconciliation, Amount
Tax at federal statutory rate	$ 192,300	$ 150,800	$ 44,800
State income tax, net of federal benefit	16,100	(8,500)	(7,100)
Change in uncertain tax positions	46,700	18,600	9,400
Foreign residual income	41,900	43,800	59,400
Nondeductible costs	16,600	20,600	10,700
Tax rate changes	2,300	1,200	(3,200)
Audit settlement	1,400	500	1,900
Income tax credits and incentives	(59,500)	(63,500)	(68,200)
Legal entity restructuring	20,100	0	0
Exclusion of tax on non-controlling interests	(15,600)	(12,500)	(9,400)
Valuation allowance	(11,800)	(12,600)	16,600
Tax exempt income	(2,100)	(2,500)	(3,300)
Foreign tax rate differential	(1,100)	(2,800)	200
Return to provision	(500)	(3,700)	(500)
ACAP investment sale	0	20,200	0
Other items, net	(2,600)	3,300	4,800
Total income tax expense	$ 204,018	$ 152,900	$ 56,052
Rate Reconciliation, Percentage
Tax at federal statutory rate (as percent)	21.00%	21.00%	21.00%
State income tax, net of federal benefit (as percent)	1.80%	(1.20%)	(3.30%)
Change in uncertain tax positions (as percent)	5.10%	2.60%	4.40%
Foreign residual income (as percent)	4.60%	6.10%	27.80%
Nondeductible costs (as percent)	1.80%	2.90%	5.00%
Tax rate changes (as percent)	0.30%	0.20%	(1.50%)
Audit settlement (as percent)	0.10%	0.10%	0.90%
Income tax credits and incentive (as percent)	(6.50%)	(8.80%)	(31.90%)
Legal entity restructuring (as percent)	(2.20%)	0.00%	0.00%
Exclusion of tax on non-controlling interests (as percent)	(1.70%)	(1.70%)	(4.40%)
Valuation allowance (as percent)	(1.30%)	(1.80%)	7.80%
Tax exempt income (as percent)	(0.20%)	(0.40%)	(1.50%)
Foreign tax rate differential (as percent)	(0.10%)	(0.40%)	0.10%
Return to provision (as percent)	(0.10%)	(0.50%)	(0.20%)
ACAP investment sale (as percent)	0.00%	2.80%	0.00%
Other items, net (as percent)	(0.30%)	0.40%	2.10%
Total income tax expense (as percent)	22.30%	21.30%	26.30%

Reportable Segments and Geographic Information - Narrative (Details)	12 Months Ended
	Sep. 30, 2025 segment
Segment Reporting [Abstract]
Number of reportable segments	3

Joint Ventures and Variable Interest Entities

12 Months Ended

Sep. 30, 2025

Joint Ventures and Variable Interest Entities [Abstract]

Joint Ventures and Variable Interest Entities

The Company’s joint ventures provide architecture, engineering, program management, construction management, operations and maintenance services, and invest in real estate projects. Joint ventures, the combination of two or more partners, are generally formed for a specific project. Management of the joint venture is typically controlled by a joint venture executive committee, comprised of representatives from the joint venture partners. The joint venture executive committee normally provides management oversight and controls decisions which could have a significant impact on the joint venture.

Some of the Company’s joint ventures have no employees and minimal operating expenses. For these joint ventures, the Company’s employees perform work for the joint venture, which is then billed to a third-party customer by the joint venture. These joint ventures function as pass-through entities to bill the third-party customer. For consolidated joint ventures of this type, the Company records the entire amount of the services performed and the costs associated with these services, including the services provided by the other joint venture partners, in the Company’s result of operations. For certain of these joint ventures where a fee is added by an unconsolidated joint venture to client billings, the Company’s portion of that fee is recorded in equity in earnings of joint ventures.

The Company also has joint ventures that have their own employees and operating expenses, and to which the Company generally makes a capital contribution. The Company accounts for these joint ventures either as consolidated entities or equity method investments based on the criteria further discussed below.

The Company follows guidance on the consolidation of variable interest entities (VIEs) that requires companies to utilize a qualitative approach to determine whether it is the primary beneficiary of a VIE. The process for identifying the primary beneficiary of a VIE requires consideration of the factors that indicate a party has the power to direct the activities that most significantly impact the joint venture’s economic performance, including powers granted to the joint venture’s program manager, powers contained in the joint venture governing board and, to a certain extent, a company’s economic interest in the joint venture. The Company analyzes its joint ventures and classifies them as either:

•a VIE that must be consolidated because the Company is the primary beneficiary or the joint venture is not a VIE and the Company holds the majority voting interest with no significant participative rights available to the other partners; or

•a VIE that does not require consolidation and is treated as an equity method investment because the Company is not the primary beneficiary or the joint venture is not a VIE and the Company does not hold the majority voting interest.

As part of the above analysis, if it is determined that the Company has the power to direct the activities that most significantly impact the joint venture’s economic performance, the Company considers whether or not it has the obligation to absorb losses or rights to receive benefits of the VIE that could potentially be significant to the VIE.

Contractually required support provided to the Company’s joint ventures is further discussed in Note 18.

Summary of financial information of the consolidated joint ventures was as follows:


	September 30, 2025		September 30, 2024

	(in millions)
Current assets	$	699.0	$	836.9
Non-current assets	84.4		83.1
Total assets	$	783.4	$	920.0

Current liabilities	$	591.4	$	763.6
Non-current liabilities	5.7		1.5
Total liabilities	597.1		765.1
Total AECOM deficit	(15.9)		(17.2)
Noncontrolling interests	202.2		172.1
Total owners’ equity	186.3		154.9
Total liabilities and owners’ equity	$	783.4	$	920.0

Total revenue of the consolidated joint ventures was $1,698.4 million, $2,242.8 million, and $1,984.3 million for the years ended September 30, 2025, 2024 and 2023, respectively. The assets of the Company’s consolidated joint ventures are restricted for use only by the particular joint venture and are not available for the general operations of the Company.

Summary of unaudited financial information of the unconsolidated joint ventures, as derived from their unaudited financial statements, was as follows:


	September 30, 2025		September 30, 2024

	(in millions)
Current assets	$	1,537.7	$	1,379.0
Non-current assets	708.0		799.9
Total assets	$	2,245.7	$	2,178.9

Current liabilities	$	1,107.8	$	976.3
Non-current liabilities	92.4		114.8
Total liabilities	1,200.2		1,091.1
Joint ventures’ equity	1,045.5		1,087.8
Total liabilities and joint ventures’ equity	$	2,245.7	$	2,178.9

AECOM’s investment in joint ventures	$	138.1	$	138.1


	Twelve Months Ended
	September 30, 2025		September 30, 2024

	(in millions)
Revenue	$	2,887.6	$	2,145.8
Cost of revenue	2,822.5		1,972.1
Gross profit	$	65.1	$	173.7
Net income	$	67.1	$	168.6

Summary of AECOM’s equity in earnings of unconsolidated joint ventures is as follows:


	Fiscal Year Ended
	September 30, 2025		September 30, 2024		September 30, 2023

	(in millions)
Pass-through joint ventures	$	27.6	$	29.0	$	24.5
Other joint ventures	(0.6)		(26.9)		(303.9)
Total	$	27.0	$	2.1	$	(279.4)

The Company completed a transaction that transitioned the AECOM Capital team to a new third-party platform in the third quarter of fiscal 2024. The team will continue to support AECOM Capital’s investment vehicles pursuant to certain advisory agreements in a manner consistent with their current obligations. During the third quarter of fiscal 2023, the Company identified indicators of impairment in the equity method investments held in its AECOM Capital segment. Specifically, the Company identified evidence that the carrying value of certain of the investments in its real estate portfolio were in excess of their fair values. The Company concluded it no longer had the intent to retain certain of these investments for a period of time sufficient to allow for an anticipated recovery in market value. In the third quarter of fiscal 2023, the Company recorded an impairment loss of $307.0 million to reduce the carrying value of these investments to their estimated fair values. During the first quarter of fiscal 2024, the Company recorded an additional impairment loss of $35.9 million. These impairments do not relate to investments in respect of which affiliates of AECOM Capital provide advisory services or manage third party capital. AECOM Capital will continue to manage existing investment vehicles and investments in a manner consistent with their current obligations. Fair value was determined using Level 3 inputs such as forecasted cash flows and comparable sales prices.

Debt

12 Months Ended

Sep. 30, 2025

Debt Disclosure [Abstract]

Debt

Debt consisted of the following:


	September 30, 2025		September 30, 2024

	(in millions)
Credit Agreement	$	1,439.9	$	1,446.6
2027 Senior Notes	—		997.3
2033 Senior Notes	1,200.0		—
Other debt	103.8		95.9
Total debt	2,743.7		2,539.8
Less: Current portion of debt and short-term borrowings	(66.3)		(66.9)
Less: Unamortized debt issuance costs	(30.2)		(22.6)
Long-term debt	$	2,647.2	$	2,450.3

The following table presents, in millions, scheduled maturities of the Company’s debt as of September 30, 2025:


Fiscal Year
2026	$	66.3
2027	31.2
2028	22.1
2029	761.3
2030	6.8
Thereafter	1,856.0
Total	$	2,743.7

Credit Agreement

On April 19, 2024, the Company entered into Amendment No. 14 to Syndicated Facility Agreement (as amended, modified or otherwise supplemented, the “Credit Agreement”), pursuant to which the Company obtained a new $$1,500,000,000 revolving credit facility (the “New Revolving Credit Facility”), a new $750,000,000 term loan A facility (the “New Term A Facility” and, together with the New Revolving Credit Facility, the “New Pro Rata Facilities”) and a new $700,000,000 term loan B facility (the “New Term B Facility” and, together with the New Pro Rata Facilities, the “New Credit Facilities”). The New Revolving Credit Facility and the New Term A Facility mature on April 19, 2029. The New Term B Facility matures on April 19, 2031. The New Term A Facility and the New Term B Facility were borrowed in full on April 19, 2024 in U.S. dollars. Loans under the New Revolving Credit Facility may be borrowed, and letters of credit thereunder may be issued, in U.S. dollars or in certain foreign currencies. The New Credit Facilities replace in full the Company’s then-existing revolving credit facility, term loan A facility and term loan B facility, and borrowings under the New Credit Facilities were used to refinance in full the Company’s existing credit facilities and for general corporate purposes. The Credit Agreement permits the Company to designate certain of its subsidiaries as additional co-borrowers from time to time. Currently, there are no co-borrowers under the New Credit Facilities. On October 29, 2024, the Company entered into Amendment No. 15 to Syndicated Facility Agreement, pursuant to which the Company reduced the interest rate spread applicable to its New Term B Facility.

Borrowings under (a) the New Revolving Credit Facility (in U.S. dollars) and the New Term A Facility bear interest at a rate per annum equal to, at the Company’s option, (i) a Term SOFR rate (with a 0% floor and SOFR adjustment of 0.10%) or (ii) a base rate (with a 0% floor), in each case, as of September 30, 2025, plus an applicable margin of 1.225% in the case of the Term SOFR rate and 0.225% in the case of the base rate, and (b) the New Revolving Credit Facility in currencies other than U.S. dollars bear interest at a rate per annum equal to the applicable reference rate for such currency (including any related adjustments), plus an applicable margin of 1.225%. The applicable margin is subject, in each case, to adjustment based on the Company’s consolidated leverage ratio from time to time.

Borrowings under the New Term B Facility, after giving effect to Amendment No. 15 to Syndicated Facility Agreement, bear interest at a rate per annum equal to, at the Company’s option, (a) a Term SOFR rate (with a 0% floor and a SOFR adjustment of 0%) or (b) a base rate (with a 0% floor), in each case, plus an applicable margin of 1.75% in the case of the Term SOFR rate and 0.75% in the case of the base rate.

Certain of the Company’s material subsidiaries (the “Guarantors”) have guaranteed the Company’s obligations of the borrowers under the Credit Agreement, subject to certain exceptions. The borrowers’ obligations under the Credit Agreement are secured by a lien on substantially all of the Company’s assets and its Guarantors’ assets, subject to certain exceptions.

The Credit Agreement contains customary negative covenants that include, among other things, limitations on the ability of the Company and certain of its subsidiaries, subject to certain exceptions, to incur liens and debt, make investments, dispositions, and restricted payments, change the nature of their business, consummate mergers, consolidations and the sale of all or substantially all of their respective assets and transact with affiliates. The Company is also required to maintain a consolidated leverage ratio of less than or equal to 4.00 to 1.00 (subject to certain adjustments in connection with permitted acquisitions), tested on a quarterly basis (the “Financial Covenant”). The Financial Covenant does not apply to the New Term B Facility. As of September 30, 2025, the Company was in compliance with the covenants of the Credit Agreement.

The Credit Agreement contains customary affirmative covenants, including, among other things, compliance with applicable law, preservation of existence, maintenance of properties and of insurance, and keeping proper books and records. The Credit Agreement contains customary events of default, including, among other things, nonpayment of principal, interest or fees, cross-defaults to other debt, inaccuracies of representations and warranties, failure to perform covenants, events of bankruptcy and insolvency, change of control and unsatisfied judgments, subject in certain cases to notice and cure periods and other exceptions.

At September 30, 2025 and September 30, 2024, letters of credit totaled $4.4 million and $4.4 million, respectively, under the Company’s New Revolving Credit Facility. As of September 30, 2025 and September 30, 2024, the Company had $1,495.6 million and $1,495.6 million, respectively, available under its New Revolving Credit Facility.

2027 Senior Notes

On February 21, 2017, the Company completed a private placement offering of $1,000,000,000 aggregate principal amount of its unsecured 5.125% Senior Notes due 2027 (the “2027 Senior Notes”). On June 30, 2017, the

Company completed an exchange offer to exchange the unregistered 2027 Senior Notes for registered notes, as well as related guarantees. In July 2025, the Company used a portion of the proceeds of the 2033 Senior Notes (defined below) to purchase $732,914,000 in principal amount of the 2027 Senior Notes that were validly tendered and not validly withdrawn at or prior to the expiration date of the tender offer for the 2027 Senior Notes. In August 2025, the Company redeemed the remaining 2027 Senior Notes with a portion of the proceeds of the 2033 Senior Notes. The purchase and redemption included an aggregate make-whole payment of $9.1 million.

2033 Senior Notes

On July 22, 2025, the Company completed an offering of $1,200,000,000 aggregate principal amount of its 6.000% Senior Notes due 2033 (the “2033 Senior Notes”). As of September 30, 2025, the estimated fair value of the 2033 Senior Notes was approximately $1,227.0 million. The fair value of the 2033 Senior Notes as of September 30, 2025 was derived by taking the mid-point of the trading prices from an observable market input (Level 2) in the secondary bond market and multiplying it by the outstanding balance of the 2033 Senior Notes.

Interest will be payable on the 2033 Senior Notes at a rate of 6.000% per annum. Interest on the 2033 Senior Notes will be payable semi-annually in arrears on February 1 and August 1 of each year, commencing on February 1, 2026. The 2033 Senior Notes will mature on August 1, 2033.

Prior to August 1, 2028, the Company may redeem all or part of the 2033 Senior Notes at a redemption price equal to 100% of the principal amount to be redeemed, plus a “make whole” premium as of the redemption date, and accrued and unpaid interest to, but excluding, the redemption date. In addition, prior to August 1, 2028, the Company may redeem up to 40% of the aggregate principal amount of the 2033 Senior Notes with proceeds from certain equity offerings at a redemption price equal to 106% of the principal amount to be redeemed, plus accrued and unpaid interest to, but excluding, the redemption date. Furthermore, at any time on or after August 1, 2028, the Company may redeem on one or more occasions all or part of the 2033 Senior Notes at the redemption prices set forth below, plus accrued and unpaid interest thereon to, but excluding, the redemption date, if redeemed during the 12-month period beginning on August 1 of each of the years indicated below:


	Percentage
2028	103.000	%
2029	101.500	%
2030 and thereafter	100.000	%

The indenture pursuant to which the 2033 Senior Notes were issued contained customary events of default, including, among other things, payment default, failure to provide certain notices thereunder and certain provisions related to bankruptcy events. The indenture also contained customary negative covenants.

Other Debt and Other Items

Other debt consists primarily of obligations under capital leases and loans, and unsecured credit facilities. The Company’s unsecured credit facilities are primarily used for standby letters of credit issued in connection with general and professional liability insurance programs and for contract performance guarantees. At September 30, 2025 and September 30, 2024, these outstanding standby letters of credit totaled $899.4 million and $934.5 million, respectively. As of September 30, 2025, the Company had $367.4 million available under these unsecured credit facilities.

Effective Interest Rate

The Company’s average effective interest rate on its total debt, including the effects of the interest rate swap and interest rate cap agreements, during the years ended September 30, 2025, 2024 and 2023 was 5.1%, 5.6% and 5.3%, respectively.

Interest expense in the consolidated statements of operations included amortization of deferred debt issuance costs for the years ended September 30, 2025, 2024 and 2023 of $7.4 million, $7.6 million and $4.9 million, respectively.

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Income Taxes

12 Months Ended

Sep. 30, 2025

Income Tax Disclosure [Abstract]

Income Taxes

Income before income taxes included income from domestic operations of $392.7 million, $233.0 million, and loss of $129.2 million for fiscal years ended September 30, 2025, 2024 and 2023 and income from foreign operations of $522.9 million, $485.2 million, and $342.6 million for fiscal years ended September 30, 2025, 2024 and 2023.

Income tax expense was comprised of:


	Fiscal Year Ended
	September 30, 2025		September 30, 2024		September 30, 2023

	(in millions)
Current:
Federal	$	88.9	$	15.1	$	67.7
State	26.4		(78.6)		71.9
Foreign	56.1		63.5		52.8
Total current income tax expense	171.4		—		192.4
Deferred:
Federal	7.7		45.2		(71.8)
State	(6.5)		68.1		(84.3)
Foreign	31.4		39.6		19.8
Total deferred income tax expense (benefit)	32.6		152.9		(136.3)
Total income tax expense	$	204.0	$	152.9	$	56.1

The major elements contributing to the difference between the U.S. federal statutory rate of 21% for fiscal years ended September 30, 2025, 2024 and 2023 and the effective tax rate are as follows:


	Fiscal Year Ended
	September 30, 2025				September 30, 2024				September 30, 2023
	Amount		%		Amount		%		Amount		%

	(in millions)
Tax at federal statutory rate	$	192.3	21.0	%	$	150.8	21.0	%	$	44.8	21.0	%
State income tax, net of federal benefit	16.1		1.8		(8.5)		(1.2)		(7.1)		(3.3)
Change in uncertain tax positions	46.7		5.1		18.6		2.6		9.4		4.4
Foreign residual income	41.9		4.6		43.8		6.1		59.4		27.8
Nondeductible costs	16.6		1.8		20.6		2.9		10.7		5.0
Tax rate changes	2.3		0.3		1.2		0.2		(3.2)		(1.5)
Audit settlement	1.4		0.1		0.5		0.1		1.9		0.9
Income tax credits and incentives	(59.5)		(6.5)		(63.5)		(8.8)		(68.2)		(31.9)
Legal entity restructuring	(20.1)		(2.2)		—		—		—		—
Exclusion of tax on non-controlling interests	(15.6)		(1.7)		(12.5)		(1.7)		(9.4)		(4.4)
Valuation allowance	(11.8)		(1.3)		(12.6)		(1.8)		16.6		7.8
Tax exempt income	(2.1)		(0.2)		(2.5)		(0.4)		(3.3)		(1.5)
Foreign tax rate differential	(1.1)		(0.1)		(2.8)		(0.4)		0.2		0.1
Return to provision	(0.5)		(0.1)		(3.7)		(0.5)		(0.5)		(0.2)
ACAP investment sale	—		—		20.2		2.8		—		—
Other items, net	(2.6)		(0.3)		3.3		0.4		4.8		2.1
Total income tax expense	$	204.0	22.3	%	$	152.9	21.3	%	$	56.1	26.3	%

During fiscal 2025, the Company recorded a reserve of $47.0 million related to uncertain tax positions associated with federal and state tax credits claimed for years subject to examination by the tax authorities. The reserve reflects the Company’s assessment that it is more likely than not that a portion of the credits may not be sustained under examination based on recent discussions and developments related to our ongoing audits.

During fiscal 2025, the Company recognized deferred tax assets of $20.1 million related to legal entity restructuring. The restructuring resulted in the recognition of deferred tax assets related to tax attributes that are expected to be utilized against future taxable income.

During fiscal 2024, the Company recorded an increase in tax benefit of $38.4 million related to state income taxes due to apportionment factor changes for fiscal years 2016 through 2023. This benefit was partially offset by an increase in tax expense of $23.0 million related to uncertain tax positions.

During fiscal 2024, the Company sold certain ACAP investments and recorded a reduction in valuation allowances of $21.0 million and a reduction in deferred tax assets of $20.2 million. In addition, the Company recorded a valuation allowance of $9.3 million related to the remaining ACAP investments.

During fiscal 2024, the Company approved a tax planning strategy and restructured certain operations in Canada which resulted in a release of a valuation allowance related to net operating losses and other deferred tax assets of $11.7 million.

During fiscal 2024, the Company settled its tax audit in Hong Kong for fiscal year 2011 through fiscal year 2021 and recorded a tax benefit of $6.9 million due primarily to changes in uncertain tax positions.

During fiscal 2023, valuation allowances in the amount of $21.0 million related to the ACAP impairment charge were established for the portion of the charge that is not expected to be realized.

The Company is currently under tax audit in several jurisdictions including the U.S. where its federal income tax returns for fiscal 2017 through 2020 are being examined by the IRS. Disputes can arise with tax authorities involving issues related to the timing of deductions, the calculation and use of credits, and the taxation of income in various tax jurisdictions because of differing interpretations or application of tax laws, regulations, and relevant facts. The IRS is currently auditing certain tax credits and the methodology for calculating the credits. We will continue to monitor developments related to the examination and will adjust the reserve as necessary based on changes in facts and circumstances, including the resolution of the audit.

Generally, the Company would reverse its valuation allowance in a particular tax jurisdiction if the positive evidence examined, such as projected and sustainable earnings or a tax-planning strategy that allows for the usage of the deferred tax asset, is sufficient to overcome significant negative evidence, such as large net operating loss carryforwards or a cumulative history of losses in recent years. In the United States, the valued deferred tax assets have a restricted life or use under relevant tax law. In addition, the Company is continually investigating tax planning strategies that, if prudent and feasible, may be implemented to realize a deferred tax asset that would otherwise expire unutilized. The identification and internal/external approval (as relevant) of such a prudent and feasible tax planning strategy could cause a reduction in the valuation allowance.

The deferred tax assets (liabilities) are as follows:


	Fiscal Year Ended
	September 30, 2025		September 30, 2024

	(in millions)
Deferred tax assets:
Compensation and benefit accruals not currently deductible	$	81.8	$	85.4
Net operating loss carryforwards	99.2		107.5
Self-insurance reserves	66.6		38.3
Research and experimentation and other tax credits	34.3		67.1
Pension liability	23.5		34.9
Accrued liabilities	263.3		265.7
Capital loss carryforward	13.0		49.5
Partnership investment	15.5		22.3
Other	12.2		8.2
Total deferred tax assets	609.4		678.9
Deferred tax liabilities:
Unearned revenue	(31.0)		(4.1)
Depreciation and amortization	(58.9)		(83.7)
Acquired intangible assets	(39.6)		—
Investment in subsidiaries	(9.8)		(9.9)
Right of use assets	(82.4)		(85.2)
Contingent consideration	—		(30.5)
Other	(3.3)		(5.4)
Total deferred tax liabilities	(225.0)		(218.8)
Valuation allowance	(157.1)		(160.9)
Net deferred tax assets	$	227.3	$	299.2

As of September 30, 2025, and 2024, the Company has available unused federal, foreign and state net operating loss (NOL) carryforwards of $700.7 million and $744.6 million, respectively, which expire at various dates over the next several years and capital loss carryforwards of $51.7 million and $181.2 million, respectively, which expire over the next five years; some foreign NOL carryforwards never expire. In addition, as of September 30, 2025, the Company has unused state and foreign research and development credits of $30.5 million and $0.2 million, respectively, and other credits of $3.7 million which expire at various dates over the next several years.

As of September 30, 2025, and 2024, gross deferred tax assets were $609.4 million and $678.9 million, respectively. The Company has recorded a valuation allowance of $157.1 million and $160.9 million as of September 30, 2025 and 2024, respectively, primarily related to foreign and state net operating loss carryforwards, capital loss carryforwards, tax credits and other deferred tax assets. The Company has performed an assessment of positive and negative evidence, including the nature, frequency, and severity of cumulative financial reporting losses in recent years, the future reversal of existing temporary differences, predictability of future taxable income exclusive of reversing temporary differences of the character necessary to realize the asset, relevant carryforward periods, taxable income in carry-back years if carry-back is permitted under tax law, and prudent and feasible tax planning strategies that would be implemented, if necessary, to protect against the loss of the deferred tax asset that would otherwise expire. Although realization is not assured, based on the Company’s assessment, the Company has concluded that it is more likely than not that the remaining gross deferred tax asset (exclusive of deferred tax liabilities) of $452.3 million will be realized and, as such, no additional valuation allowance has been provided. The net decrease in the valuation allowance of $3.8 million is primarily attributable to a decrease in valuation allowances of $5.6 million related to the capital losses, and an increase in valuation allowances on foreign net operating losses and currency translation adjustments of $1.9 million.

Generally, the Company does not provide for U.S. taxes or foreign withholding taxes on gross book-tax differences in its non-U.S. subsidiaries because such basis differences of approximately $1.1 billion are able to and intended to be reinvested indefinitely. If these basis differences were distributed, foreign tax credits could become available

under current law to partially or fully reduce the resulting U.S. income tax liability. There may also be additional U.S. or foreign income tax liability upon repatriation, although the calculation of such additional taxes is not practicable.

As of September 30, 2025, and 2024, the Company had a liability for unrecognized tax benefits, including potential interest and penalties, net of related tax benefit, totaling $144.1 million and $97.9 million, respectively. The gross unrecognized tax benefits as of September 30, 2025 and 2024 were $129.6 million and $81.3 million, respectively, excluding interest, penalties, and related tax benefit. Of the $129.6 million, approximately $125.4 million would be included in the effective tax rate if recognized. A reconciliation of the beginning and ending amount of gross unrecognized tax benefits is as follows:


	Fiscal Year Ended
	September 30, 2025		September 30, 2024

	(in millions)
Balance at the beginning of the year	$	81.3	$	62.1
Gross increase in current period’s tax positions	9.2		34.5
Gross increase in prior years’ tax positions	47.0		13.9
Gross decrease in prior years’ tax positions	(6.4)		(20.1)
Decrease due to settlement with tax authorities	—		(7.4)
Decrease due to lapse of statute of limitations	(1.3)		(2.2)
Gross change due to foreign exchange fluctuations	(0.2)		0.5
Balance at the end of the year	$	129.6	$	81.3

The Company classifies interest and penalties related to uncertain tax positions within the income tax expense line in the accompanying consolidated statements of operations. As of September 30, 2025, the accrued interest and penalties were $23.8 million and $3.2 million, respectively, excluding any related income tax benefits. As of September 30, 2024, the accrued interest and penalties were $27.7 million and $3.5 million, respectively, excluding any related income tax benefits.

The Company files income tax returns in numerous tax jurisdictions, including the U.S., and numerous U.S. states and non-U.S. jurisdictions around the world. The statute of limitations varies by jurisdiction in which the Company operates. Because of the number of jurisdictions in which the Company files tax returns, in any given year the statute of limitations in certain jurisdictions may expire without examination within the 12-month period from the balance sheet date.

While it is reasonably possible that the total amounts of unrecognized tax benefits could significantly increase or decrease within the next twelve months, an estimate of the range of possible change cannot be made.

- Definition

The entire disclosure for income tax.

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-URI https://asc.fasb.org/1943274/2147482603/740-30-50-2

+ Details

Discontinued Operations, Goodwill and Intangible Assets - Schedule of Changes in Carrying Value of Goodwill by Reportable Segment (Details) $ in Thousands	12 Months Ended
	Sep. 30, 2025 USD ($)
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 3,480,155
Foreign Exchange Impact	(5,000)
Acquired	225,400
Goodwill, ending balance	3,700,619
Americas
Goodwill [Roll Forward]
Goodwill, beginning balance	2,625,700
Foreign Exchange Impact	(5,400)
Acquired	150,100
Goodwill, ending balance	2,770,400
International
Goodwill [Roll Forward]
Goodwill, beginning balance	854,500
Foreign Exchange Impact	400
Acquired	75,300
Goodwill, ending balance	$ 930,200

- Definition

Amount, after accumulated impairment loss, of asset representing future economic benefit arising from other asset acquired in business combination or from joint venture formation or both, that is not individually identified and separately recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 24
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482548/350-20-55-24

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Reference 3: http://www.xbrl.org/2003/role/exampleRef
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Reference 14: http://www.xbrl.org/2009/role/commonPracticeRef
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-Publisher FASB
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+ Details

Insider Trading Policies and Procedures	3 Months Ended
Insider Trading Policies and Procedures	Sep. 30, 2025
Insider Trading Policies and Procedures [Line Items]
Insider Trading Policies and Procedures Adopted	true

Earnings Per Share (Tables)

12 Months Ended

Sep. 30, 2025

Earnings Per Share [Abstract]

Schedule of Reconciliation of Denominators for Basic and Diluted Earnings Per Share

The following table sets forth a reconciliation of the denominators of basic and diluted earnings per share:


	Fiscal Year Ended
	September 30, 2025	September 30, 2024	September 30, 2023

	(in millions)
Denominator for basic earnings per share	132.4	135.5	138.6
Potential common shares	0.9	1.0	1.5
Denominator for diluted earnings per share	133.3	136.5	140.1