Amentum's Mullen receives 4,839 vested shares

Q: How many AMTM shares did Sean Thomas Mullen receive when his restricted stock units vested?

Sean Thomas Mullen received 4,839 common shares upon vesting on November 6, 2026.

Q: How many AMTM shares were withheld for Sean Thomas Mullen's tax withholding?

2,183 common shares were tendered for tax withholding upon vesting on November 6, 2026, at a reported price of $21.25 per share.

The restricted stock units are scheduled to vest in one-third installments on each of the first, second and third anniversaries of the grant date.

Available on EDGAR 11/10/2026 - 05:54 PM EST Accepted by SEC EDGAR 11/10/2026 - 05:53 PM EST

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Form Type

Rhea-AI Filing Summary

Amentum Holdings, Inc. Chief Growth Officer Sean Thomas Mullen reported vesting of 4,839 restricted stock units and distribution of 4,839 common shares on November 6, 2026. The report also records 2,183 common shares tendered for tax withholding upon vesting at a reported $21.25 per share. The reported resulting position was 4,839 restricted stock units.

Insider Trade Summary

4,839 shares exercised/converted

Exercise 3 txns

Insider Mullen Sean Thomas

Role Chief Growth Officer

Type	Security	Shares	Price	Value
Exercise	Restricted Stock Units ^{F3, F4}	4,839	$0.00	$0.00
Exercise	Common Stock ^F1	4,839	--	--
Tax Withholding	Common Stock ^F2	2,183	$21.25	$46K

Holdings After Transaction: Restricted Stock Units — 4,839 units (Direct); Common Stock — 35,104 shares (Direct)

Holdings Before and After: Restricted Stock Units, 9,678 to 4,839 units (Direct); Common Stock, 32,448 to 35,104 shares (Direct)

Footnotes (4)

F1. Represents distribution of AMTM common stock upon vesting of restricted stock units.
F2. Represents number of shares of AMTM common stock tendered for tax withholding upon vesting of restricted stock units.
F3. Each restricted stock unit represents a contingent right to receive one share of AMTM common stock.
F4. One-third of the restricted stock units shall vest and be delivered, net of tax withholding, on each of the first, second and third anniversaries of the date of grant.

Key Figures

Common shares distributed: 4,839 shares Shares tendered for tax withholding: 2,183 shares Reported price per share for tax withholding: $21.25 per share +1 more

4 metrics

Common shares distributed 4,839 shares Upon vesting on November 6, 2026

Shares tendered for tax withholding 2,183 shares Upon vesting on November 6, 2026

Reported price per share for tax withholding $21.25 per share November 6, 2026

RSUs following transaction 4,839 RSUs Reported resulting position

Key Terms

Restricted Stock Units, tax withholding, contingent right

3 terms

Restricted Stock Units financial

"Represents distribution of AMTM common stock upon vesting of restricted stock units."

Restricted stock units are a type of company reward where employees are promised shares of stock, but they only fully own these shares after meeting certain conditions, like staying with the company for a set time. They matter because they can become valuable assets and are often used to motivate employees to help the company succeed.

tax withholding financial

"Represents number of shares of AMTM common stock tendered for tax withholding upon vesting"

Tax withholding is the practice of taking a portion of a payment—such as wages, dividends, or sale proceeds—before it reaches the recipient and sending that portion to the tax authority as an advance on the recipient’s eventual tax bill. For investors it matters because withholding reduces immediate cash received and affects after‑tax returns, estimated tax payments, and whether you may owe more or receive a refund when taxes are finally calculated, like having a small automatic savings set aside for your tax bill.

contingent right financial

"Each restricted stock unit represents a contingent right to receive one share of AMTM common stock."

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

How many AMTM shares did Sean Thomas Mullen receive when his restricted stock units vested?

Sean Thomas Mullen received 4,839 common shares upon vesting on November 6, 2026.

How many AMTM shares were withheld for Sean Thomas Mullen's tax withholding?

2,183 common shares were tendered for tax withholding upon vesting on November 6, 2026, at a reported price of $21.25 per share.

AI-generated analysis. How Rhea-AI works. Not financial advice.

Form 4 Insider Transactions: What Each Field Means →

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SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Mullen Sean Thomas

(Last)

(First)

(Middle)

C/O AMENTUM HOLDINGS, INC.

4800 WESTFIELDS BOULEVARD, SUITE 400

(Street)

CHANTILLY

VIRGINIA

20151

(City)

(State)

(Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
Amentum Holdings, Inc. [ AMTM ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

	Director	10% Owner
X	Officer (give title below)	Other (specify below)
	Chief Growth Officer

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
11/06/2026

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

4. If Amendment, Date of Original Filed (Month/Day/Year)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	Amount	(A) or (D)	Price		6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
Common Stock	11/06/2026		M		4,839	A	⁽¹⁾	37,287	D
Common Stock	11/06/2026		F		2,183⁽²⁾	D	$21.25	35,104	D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	8. Price of Derivative Security (Instr. 5)		10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
Restricted Stock Units	⁽³⁾	11/06/2026		M			4,839	⁽⁴⁾	⁽⁴⁾	Common Stock	4,839	$0	4,839	D

Explanation of Responses:

1. Represents distribution of AMTM common stock upon vesting of restricted stock units.

2. Represents number of shares of AMTM common stock tendered for tax withholding upon vesting of restricted stock units.

3. Each restricted stock unit represents a contingent right to receive one share of AMTM common stock.

4. One-third of the restricted stock units shall vest and be delivered, net of tax withholding, on each of the first, second and third anniversaries of the date of grant.

Remarks:

	/s/ Indira Lall, Attorney-in-fact	11/10/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.
* Form 4: SEC 1474 (03-26)

Source: View Original Filing on SEC EDGAR