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  4. [Form 4] MERCURY SYSTEMS INC Insider Trading Activity

Mercury Systems CEO sells 48,812 shares for taxes

MERCURY SYSTEMS INC (MRCY) reported that Chairman, President & CEO William L. Ballhaus sold a total of 48,812 shares of common stock on August 19–20, 2026 at weighted prices of $100.3060 and $97.6734 per share.

Filing Impact
(Very High)
Filing Sentiment
(Negative)
Form Type
4

Rhea-AI Filing Summary

MERCURY SYSTEMS INC (MRCY) reported that Chairman, President & CEO William L. Ballhaus sold a total of 48,812 shares of common stock on August 19–20, 2026 at weighted prices of $100.3060 and $97.6734 per share. Footnotes state these sales were made under a sell-to-cover program to satisfy tax withholding obligations upon vesting of stock awards. After these transactions, he continues to hold shares indirectly, including 1,403 shares in a 401K Plan and 7,066.173 shares through Milestone Road Holdings, LLC.

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Insights

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Insider Ballhaus William L
Role Chairman, President & CEO
Sold 48,812 shs ($4.84M)
Type Security Shares Price Value
Sale Common Stock F1, F2 22,010 $97.6734 $2.15M
Sale Common Stock F1, F2 26,802 $100.306 $2.69M
holding Common Stock -- -- --
holding Common Stock -- -- --
Holdings After Transaction: Common Stock — 228,197.325 shares (Direct); Common Stock — 1,403 shares (Indirect, 401K Plan); Common Stock — 7,066.173 shares (Indirect, By Milestone Road Holdings, LLC)
Footnotes (2)
  1. F1. Represents shares sold as part of a sell-to-cover program to satisfy tax withholding obligations upon the vesting of stock awards.
  2. 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.
Shares sold August 20, 2026 22,010 shares Common Stock sale at $97.6734 per share in sell-to-cover program
Shares sold August 19, 2026 26,802 shares Common Stock sale at $100.3060 per share in sell-to-cover program
Total shares sold 48,812 shares Net shares sold across both reported sales transactions
Sale price August 20, 2026 $97.6734 per share Attributed per-share price for sell-to-cover sales on that date
Sale price August 19, 2026 $100.3060 per share Attributed per-share price for sell-to-cover sales on that date
Indirect holding in 401K Plan 1,403 shares Common Stock held indirectly through a 401K Plan after transactions
Indirect holding via Milestone Road Holdings, LLC 7,066.173 shares Common Stock held indirectly through Milestone Road Holdings, LLC
sell-to-cover program financial
"Represents shares sold as part of a sell-to-cover program"
tax withholding obligations financial
"to satisfy tax withholding obligations upon the vesting of stock awards"
401K Plan financial
"total_shares_following_transaction: "1403.0000" 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.
indirect financial
"ownership_type: "indirect" ownership_code: "I""

FAQ

What insider transactions did MRCY report for William L. Ballhaus on this Form 4?
The Form 4 reports that William L. Ballhaus sold 48,812 shares of Mercury Systems common stock on August 19–20, 2026 in open-market or private transactions, with prices of $100.3060 and $97.6734 per share, as part of a sell-to-cover program.

Why did William L. Ballhaus sell MRCY shares according to this Form 4?
The sales were made as part of a sell-to-cover program to satisfy tax withholding obligations upon the vesting of stock awards, according to the footnotes. The per-share prices reflect amounts attributed to all participants in this program on the transaction dates.

How many MRCY shares did William L. Ballhaus sell on each date?
On August 20, 2026, William L. Ballhaus sold 22,010 shares at $97.6734 per share. On August 19, 2026, he sold 26,802 shares at $100.3060 per share, all as part of a sell-to-cover program for tax withholding.

What MRCY holdings does William L. Ballhaus report after these transactions?
After the reported trades, William L. Ballhaus reports indirect ownership of 1,403 shares of Mercury Systems common stock in a 401K Plan and 7,066.173 shares held by Milestone Road Holdings, LLC, as shown in the holding entries.

Were the MRCY sales by William L. Ballhaus under a Rule 10b5-1 plan?
The document-level Rule 10b5-1 checkbox is not checked (aff_10b5_one is false). The footnotes instead describe the transactions as part of a sell-to-cover program for tax withholding, without identifying them as Rule 10b5-1 plan trades.

How is the sale price for William L. Ballhaus’s MRCY sell-to-cover transactions determined?
A footnote states the reported per-share prices represent the price attributed to sales on behalf of all participants under the sell-to-cover program on each indicated transaction date, rather than an individualized execution price for a single trade.

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SEC Form 4
FORM 4UNITED 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*
Ballhaus William L
(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)
XDirector10% Owner
XOfficer (give title below)Other (specify below)
Chairman, President & CEO
2a. Foreign Trading Symbol
3. Date of Earliest Transaction (Month/Day/Year)
08/19/2026		6. Individual or Joint/Group Filing (Check Applicable Line)
XForm 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)
CodeVAmount(A) or (D)Price
Common Stock08/19/2026S26,802(1)D$100.306(2)250,207.325D
Common Stock08/20/2026S22,010(1)D$97.6734(2)228,197.325D
Common Stock1,403I401K Plan
Common Stock7,066.173IBy Milestone Road Holdings, LLC
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)
CodeV(A)(D)Date ExercisableExpiration DateTitleAmount or Number of Shares
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, attorney-in-fact08/21/2026
** Signature of Reporting PersonDate
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