Were Douglas Munro’s MRCY share sales under a Rule 10b5-1 plan?

The report indicates the Rule 10b5-1 plan checkbox is not affirmed , and there is no specific footnote stating that these transactions were executed pursuant to a Rule 10b5-1 trading plan.

Mercury Systems (NASDAQ: MRCY) CAO sells 898 shares in tax trade

Q: What did MRCY executive Douglas Munro report in this Form 4?

Douglas Munro reported sales of 898 shares of Mercury Systems common stock in mid-August 2026. These were open-market or private sales executed under a sell-to-cover program related to vested stock awards.

Q: At what prices did Douglas Munro sell MRCY shares?

Munro reported selling 494 shares at $111.3577 on August 18, 2026, and 404 shares at $109.9509 on August 17, 2026. The per-share prices reflect amounts attributed to all participants in the sell-to-cover program.

Q: Why were MRCY shares sold by Douglas Munro in this report?

The Form 4 states the shares were sold under a sell-to-cover program to satisfy tax withholding obligations arising from the vesting of stock awards, rather than as discretionary sales of investment holdings.

Q: How many MRCY shares does Douglas Munro hold indirectly after these transactions?

Munro reports indirect ownership of 359 shares of Mercury Systems common stock through a 401K Plan as of August 17, 2026. The report does not state his total direct holdings after the sell-to-cover sales.

Filing Impact

(Neutral)

Filing Sentiment

(Negative)

Form Type

Rhea-AI Filing Summary

MERCURY SYSTEMS INC (MRCY) reported that officer Douglas Munro, SVP and Chief Accounting Officer, sold a total of 898 shares of common stock in mid-August 2026. The sales of 494 shares at $111.3577 on August 18 and 404 shares at $109.9509 on August 17 were executed as part of a sell-to-cover program to satisfy tax withholding obligations upon the vesting of stock awards. Munro also reports indirect ownership of 359 shares held in a 401K Plan.

Insider Trade Summary

Net Seller: 898 shares

Net Sell 3 txns

Insider Munro Douglas

Role SVP, CAO

Sold 898 shs ($99K)

Type	Security	Shares	Price	Value
Sale	Common Stock ^{F1, F2}	494	$111.3577	$55K
Sale	Common Stock ^{F1, F2}	404	$109.9509	$44K
holding	Common Stock	--	--	--

Holdings After Transaction: Common Stock — 13,639 shares (Direct); Common Stock — 359 shares (Indirect, 401K Plan)

Footnotes (2)

F1. Represents shares sold as part of a sell-to-cover program to satisfy tax withholding obligations upon the vesting of stock awards.
F2. Represents the per share price attributed to sales of shares on behalf of all participants under the sell-to-cover program on the transaction date indicated.

Key Figures

Shares sold August 18, 2026: 494 shares Sale price August 18, 2026: $111.3577 per share Shares sold August 17, 2026: 404 shares +3 more

6 metrics

Shares sold August 18, 2026 494 shares Common Stock sold by Douglas Munro on 2026-08-18

Sale price August 18, 2026 $111.3577 per share Attributed per-share sale price under sell-to-cover program

Shares sold August 17, 2026 404 shares Common Stock sold by Douglas Munro on 2026-08-17

Sale price August 17, 2026 $109.9509 per share Attributed per-share sale price under sell-to-cover program

Total shares sold 898 shares Aggregate of two sell-to-cover sales in August 2026

Indirect holdings (401K Plan) 359 shares Common Stock held indirectly in 401K Plan after transactions

Key Terms

sell-to-cover program, tax withholding obligations, 401K Plan

3 terms

sell-to-cover program financial

"Represents shares sold as part of a sell-to-cover program to satisfy"

tax withholding obligations financial

"program to satisfy tax withholding obligations upon the vesting"

401K Plan financial

"nature_of_ownership": "401K Plan""

A 401(k) plan is an employer-sponsored retirement savings account that lets workers set aside part of their paycheck into investments, often with tax breaks and sometimes with matching contributions from the employer. Think of it as a workplace piggy bank that grows through employee contributions, optional company top-ups, and market returns; it matters to investors because it shapes household retirement security, drives large flows of money into public markets, and affects a company’s compensation costs and ability to attract and keep talent.

FAQ

What did MRCY executive Douglas Munro report in this Form 4?

Douglas Munro reported sales of 898 shares of Mercury Systems common stock in mid-August 2026. These were open-market or private sales executed under a sell-to-cover program related to vested stock awards.

At what prices did Douglas Munro sell MRCY shares?

Munro reported selling 494 shares at $111.3577 on August 18, 2026, and 404 shares at $109.9509 on August 17, 2026. The per-share prices reflect amounts attributed to all participants in the sell-to-cover program.

Why were MRCY shares sold by Douglas Munro in this report?

The Form 4 states the shares were sold under a sell-to-cover program to satisfy tax withholding obligations arising from the vesting of stock awards, rather than as discretionary sales of investment holdings.

How many MRCY shares does Douglas Munro hold indirectly after these transactions?

Munro reports indirect ownership of 359 shares of Mercury Systems common stock through a 401K Plan as of August 17, 2026. The report does not state his total direct holdings after the sell-to-cover sales.

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

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Form 4 Insider Transactions: What Each Field Means →

Available on EDGAR 08/19/2026 - 06:32 PM Accepted by SEC EDGAR 08/19/2026 - 06:31 PM

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^*

Munro Douglas

(Last)

(First)

(Middle)

50 MINUTEMAN ROAD

(Street)

ANDOVER

MASSACHUSETTS

01810

(City)

(State)

(Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
MERCURY SYSTEMS INC [ MRCY ]

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

	Director	10% Owner
X	Officer (give title below)	Other (specify below)
	SVP, CAO

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
08/17/2026

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	08/17/2026		S		404⁽¹⁾	D	$109.9509⁽²⁾	14,133	D
Common Stock	08/18/2026		S		494⁽¹⁾	D	$111.3577⁽²⁾	13,639	D
Common Stock								359	I	401K Plan

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)

Explanation of Responses:

1. Represents shares sold as part of a sell-to-cover program to satisfy tax withholding obligations upon the vesting of stock awards.

2. Represents the per share price attributed to sales of shares on behalf of all participants under the sell-to-cover program on the transaction date indicated.

	/s/ Douglas Munro	08/19/2026
	** 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