•Time-based restricted stock units (“RSUs”) within the Amentum Holdings, Inc. 2024 Stock Incentive Plan (the “Plan”);

The Plan provides Amentum’s employees, non-employee directors and consultants the opportunity to receive various types of stock-based compensation awards including stock options, restricted stock units and performance-based awards, as well as cash awards. As of October 3, 2025, 15.9 million shares of Amentum’s common stock was reserved for future issuance under the Plan.

The fair value of the RSUs was determined based on the Company’s common stock closing price on the date of the grant. The RSUs generally vest 50% a year over two years, 33% a year over three years, 25% a year over four years or cliff vest in three years. RSU compensation expense is recognized on a straight-line basis ratably over the requisite service period, which is generally the vesting period, unless otherwise specifically noted. Amounts recognized for forfeitures are adjusted periodically to reflect actual forfeitures.

Changes in RSUs during the year ended October 3, 2025 were not significant. As of October 3, 2025, there was $27 million of unrecognized compensation expense related to the RSUs, scheduled to be recognized over a weighted-average period of 2 years. The fair value of RSUs that vested in fiscal years 2025 was $1 million. No RSUs vested in fiscal years 2024 and 2023.

As part of the Transaction, 65,182 Jacobs’ restricted stock units were converted to 342,741 of Amentum RSUs. The fair value of these RSUs was determined based on the Company’s common stock on the Transaction date.

Performance-based restricted stock units vest and the stock is issued at the end of the performance period, which can range from 1 to 3 years, based upon the achievement of specific performance conditions. If the performance does not satisfy the applicable conditions, no shares will be issued. The initial PSU grants occurred in fiscal year 2025.

Changes in PSUs during the year ended October 3, 2025 were not significant. As of October 3, 2025, there was $10 million of unrecognized compensation cost which is expected to be recognized over a weighted average of 2 years.

During fiscal year 2025, we commenced the grants of stock options. The stock options have a vesting term of 3 years with a portion vesting each year over the vesting period.

The fair value of the stock options is estimated based on the date of the grant using the Black-Scholes-Merton option-pricing model and stock option compensation expense is recognized on a straight-line basis ratably over the requisite service period, which is the vesting period.

Changes in stock options during the year ended October 3, 2025 were not significant. No stock options were provided in fiscal years 2024 and 2023.

The Company adopted the Amentum Holdings, Inc. Employee Stock Purchase Plan (“ESPP”) on September 27, 2024 and implemented the ESPP beginning July 01, 2025. The ESPP is a qualified plan under Section 423 of the Internal Revenue Code and allows eligible employees the right to purchase shares of our common stock at a 5% discount of the market value on the last day of the offering period. For financial reporting purposes, the ESPP is considered non-compensatory, therefore no stock-based compensation expense is recognized to acquire shares under the ESPP.

During fiscal year 2025, $3 million was received from ESPP plan participants for the issuance of Amentum common stock. As of October 3, 2025, participants have purchased 0.1 million shares under the ESPP, at a weighted-average price per share of $22.75. A total of 2.5 million shares remain available for future issuance under the ESPP.

Prior to the Transaction, certain members of management were awarded Time-Vested Class B units and Performance-Vested Class B units in Amentum Joint Venture LP, our previous parent company (“AJVLP” and “Amentum Equityholder”). The Time-Vested Class B units vested 20% a year over five years and the Performance-Vested Class B units vested upon the consummation of a change in control transaction and achievement of certain return metrics associated with such transaction. Both the Time-Vested Class B units and Performance-Vested Class B units were equity classified awards in Amentum Joint Venture LP.

The fair value of the Class B units was estimated based on the date of the grant using the Black-Scholes-Merton option-pricing model. We recognized compensation expense for the Time-Vested Class B units based on grant date fair values. Prior to the Transaction, compensation expense for the Time-Vested Class B units was recognized on a straight-line basis ratably over the requisite service period, which was the vesting period.

In connection with the completion of the Transaction on September 27, 2024, the unvested Time-Vested and Performance-Vested Class B units were discretionarily modified to vest in connection with the Transaction. Due to the modification, we recognized $13 million of compensation expense in the consolidated statements of operations for the year ended September 27, 2024. As of September 27, 2024, there was no unrecognized compensation expense related to the Time-Vested Class B units or the Performance-Vested Class B units. Amounts recognized for forfeitures were adjusted periodically to reflect actual forfeitures.

For the fiscal years ended September 27, 2024 and September 29, 2023, we recognized Class B unit compensation expense of $18 million and $3 million, respectively. For the fiscal years ended September 27, 2024 and September 29, 2023, there were no income tax benefits recognized from Class B unit compensation expense.


	For the years ended
(Amounts in millions)	October 3, 2025		September 27, 2024		September 29, 2023
RSUs	$	16	$	—	$	—
PSUs	4		—		—
Stock Options	1		—		—
Class B units	—		18		3
Total stock-based compensation expense	$	21	$	18	$	3
Income tax benefits recognized from stock-based compensation	$	3	$	—	$	—