Acquisition and Divestiture (Tables)

12 Months Ended

Oct. 03, 2025

Business Combination, Asset Acquisition, Transaction between Entities under Common Control, and Joint Venture Formation [Abstract]

Schedule of Preliminary Allocation of the Purchase Price

Under the acquisition method of accounting, the total final consideration exchanged for the CMS transaction is shown below and increased $7 million from September 27, 2024:

(In millions, except per share amounts)
Shares of Amentum Holdings, Inc. common stock issued to CMS shareholders	142
Per share price of Amentum Holdings, Inc. common stock	25.67
Fair value of common stock issued to CMS shareholders (1)	3,654
Fair value of additional equity consideration issued to CMS shareholders (2)	218
Final working capital settlement (3)	70
Other consideration (4)	6
Fair value of consideration transferred	3,948
Fair value of previously held equity interest (5)	84
Total consideration	$	4,032

(1)    Represents the fair value of equity consideration received by CMS shareholders to provide 58.5% ownership in the Company.

(2)    Represents the additional equity consideration which was finalized in March 2025. The balance reflects a decrease in equity consideration issued to CMS Shareholders following a resolution to release an additional 1.0% of the issued and outstanding shares of Amentum common stock back to Sponsor Stockholder. This balance is presented at fair value based on the acquisition-date share price and is included in the total purchase consideration in accordance with ASC 805.

(3)    Reflects a $70 million cash payment made based on the final net working capital position. This payment was made in the third quarter of fiscal year 2025 and included in the total purchase consideration in accordance with ASC 805, as it represents an obligation attributable to pre-acquisition activities.

(4)    Represents other immaterial adjustments, including a) estimated equity consideration related to pre-combination stock-based compensation awards, b) the settlement of CMS transaction costs paid by Amentum, and c) the removal of consideration related to the acquisition of non-controlling interests.

(5)    Prior to the Transaction, we held a non-controlling interest in a joint venture of 50% which was accounted for under the equity method of accounting, with the remaining 40% held by CMS and 10% held by an unrelated third party. As a result of the Transaction, the Company gained a controlling financial interest in the joint venture and it became a consolidated joint venture of the Company. This joint venture acquisition was accounted for as a business combination achieved in stages. Our pre-existing equity method investment in the joint venture was remeasured at an acquisition date fair value of $170 million by using a discounted cash flow model based on estimated future revenues, margins and discount rates, among other variables and estimates. The Company’s previously held equity interest in the joint venture was remeasured to fair value, resulting in a gain of $69 million recognized in the year ended September 27, 2024, which is included in gain on acquisition of controlling interest in our consolidated statements of operations. Additionally, as of the acquisition date, the Company had a payable from the joint venture with a fair value of $1 million that was settled in connection with the acquisition.

Business Combination, Recognized Asset Acquired and Liability Assumed

The final allocation of the purchase price is as follows:

(Amounts in millions)	Preliminary Allocation of Purchase Price		Measurement Period Adjustments, Net		Final Allocation of Purchase Price
Cash and cash equivalents	$	488	$	—	$	488
Accounts receivable	1,043		(64)		979
Prepaid expenses and other current assets	82		(34)		48
Property and equipment	72		(3)		69
Equity method investments	17		50		67
Goodwill	2,665		339		3,004
Intangible assets	1,860		(55)		1,805
Other long-term assets	107		37		144
Current portion of long-term debt	(8)		—		(8)
Accounts payable	(257)		(3)		(260)
Accrued compensation and benefits	(285)		22		(263)
Contract liabilities	(48)		(49)		(97)
Other current liabilities	(98)		(190)		(288)
Long-term debt, net of current portion	(1,122)		—		(1,122)
Deferred tax liabilities	(353)		61		(292)
Other long-term liabilities	(75)		(40)		(115)
Non-controlling interests	(63)		(64)		(127)
Total consideration	$	4,025	$	7	$	4,032

Schedule of Unaudited Pro Forma Financial Information

The following unaudited pro forma combined financial information presents the combined results of operations for CMS and the Company for the pre-acquisition periods of the twelve months ended September 27, 2024 and September 29, 2023, respectively:

	For the years ended
(Amounts in millions)	September 27, 2024		September 29, 2023
Revenues	$	13,858	$	13,371
Net income (loss) attributable to common shareholders	145		(170)