Standard BioTools SVP has shares withheld for taxes

STANDARD BIOTOOLS INC. executive Sean Mackay, SVP & Chief Business Officer, reported a tax-related share disposition.

Rhea-AI Filing Summary

STANDARD BIOTOOLS INC. executive Sean Mackay, SVP & Chief Business Officer, reported a tax-related share disposition. On February 23, 2026, 19,661 shares of common stock were withheld at $1.15 per share to cover tax obligations from previously granted restricted stock units that vested. After this withholding, Mackay directly holds 760,174 shares of Standard BioTools common stock. This was a tax-withholding disposition, not an open-market purchase or sale.

Insider Trade Summary

Exercise Price or Tax Liability: 19,661 shares

Exercise Price or Tax Liability 1 txn

Insider Mackay Sean

Role SVP & Chief Business Officer

Type	Security	Shares	Price	Value
Exercise Price or Tax Liability	Common Stock	19,661	$1.15	$23K

Holdings After Transaction: Common Stock — 760,174 shares (Direct)

Footnotes (1)

1. F1. The shares were withheld from the reporting person to satisfy the tax withholding obligations that arose upon the vesting of restricted stock units granted to the reporting person on May 20, 2024 and March 21, 2025, which grants were originally reported on Form 3 and Form 4 filed with the U.S. Securities and Exchange Commission on September 3, 2024 and March 24, 2025, respectively.

FAQ

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

What insider transaction did STANDARD BIOTOOLS (LAB) report for Sean Mackay?

STANDARD BIOTOOLS reported that executive Sean Mackay had 19,661 common shares withheld to satisfy tax obligations from vesting restricted stock units. This tax-withholding disposition occurred on February 23, 2026 and was not an open-market trade.

Was the STANDARD BIOTOOLS (LAB) Form 4 a stock sale by Sean Mackay?

No, the Form 4 shows a tax-withholding disposition, not an open-market stock sale. Shares were withheld by the company to cover taxes triggered when Mackay’s restricted stock units vested, a common administrative step with equity compensation.

How many STANDARD BIOTOOLS (LAB) shares were disposed of and at what price?

The filing shows 19,661 shares of STANDARD BIOTOOLS common stock were withheld at a price of $1.15 per share. The disposition was coded as “F,” indicating payment of tax liability by delivering securities related to restricted stock unit vesting.

How many STANDARD BIOTOOLS (LAB) shares does Sean Mackay hold after this transaction?

After the tax-withholding disposition, Sean Mackay directly holds 760,174 shares of STANDARD BIOTOOLS common stock. This figure reflects his remaining direct ownership following the 19,661 shares withheld to cover tax obligations tied to vesting equity awards.

What caused the tax-withholding disposition reported by STANDARD BIOTOOLS (LAB)?

The disposition resulted from restricted stock units granted to Sean Mackay on May 20, 2024 and March 21, 2025 that later vested. When these RSUs vested, tax liabilities arose, and 19,661 shares were withheld to satisfy those obligations as disclosed in the footnote.

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

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Accepted by SEC EDGAR 02/24/2026 - 05:44 PM Learn about SEC filing dates

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^*

Mackay Sean

(Last) (First) (Middle)

C/O STANDARD BIOTOOLS INC.

50 MILK STREET, 10TH FLOOR

(Street)

BOSTON MA 02109

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
STANDARD BIOTOOLS INC. [ LAB ]

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

	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	SVP & Chief Business Officer

3. Date of Earliest Transaction (Month/Day/Year)
02/23/2026

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

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

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

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)
			Code	V	Amount	(A) or (D)	Price
Common Stock	02/23/2026		F		19,661(1)	D	$1.15	760,174	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)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:

1. The shares were withheld from the reporting person to satisfy the tax withholding obligations that arose upon the vesting of restricted stock units granted to the reporting person on May 20, 2024 and March 21, 2025, which grants were originally reported on Form 3 and Form 4 filed with the U.S. Securities and Exchange Commission on September 3, 2024 and March 24, 2025, respectively.

	/s/ Sean Mackay by Tomone Tanaka, Attorney-in-Fact	02/24/2026
	** 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.