New Accounting Pronouncements and Changes in Accounting (Policies)	9 Months Ended
	Jun. 30, 2025
Accounting Standards Update and Change in Accounting Principle [Abstract]
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, 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 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.

AECOM 10-Q