LAB insider withholding of 19,661 shares to cover RSU taxes

Rhea-AI Filing Summary

Sean Mackay, SVP & Chief Business Officer of Standard BioTools Inc. (LAB), reported a disposition of 19,661 shares of common stock on 08/20/2025. The filing shows the sale was coded F and executed at $1.27 per share. The report explains these shares were withheld to satisfy tax withholding obligations arising from the vesting of restricted stock units originally granted on May 20, 2024 and March 21, 2025.

After the withholding, Mackay beneficially owns 799,496 shares, held directly. The transaction is a routine withholding to cover taxes tied to equity compensation rather than an open-market sale for other purposes.

Insights

Securities Analyst

TL;DR: Insider withheld shares to cover taxes on vested RSUs; transaction appears routine and not an active cash-sale signal.

The Form 4 documents a Code F disposition of 19,661 shares at $1.27 per share, described as tax withholding upon RSU vesting from grants dated May 20, 2024 and March 21, 2025. The reporting person retains 799,496 shares directly. From a securities-analytic perspective, such withholdings are common and typically neutral for near-term price impact because they do not reflect a deliberate decision to monetize equity beyond tax obligations.

Corporate Governance Expert

TL;DR: Transaction is administrative (tax withholding) tied to equity compensation and raises no governance red flags.

The disclosure clearly states the disposition was to satisfy tax withholding on vested restricted stock units. The reporting person is an officer and director-level executive, and the form indicates direct ownership of 799,496 shares after the withholding. There is no indication of unusual timing, related-party transfer, or change in officer status in this filing; governance implications are therefore limited.

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.

2 TOWER PLACE, STE 2000

(Street)

SOUTH SAN FRANCISCO CA 94080

(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)
08/20/2025

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	08/20/2025		F		19,661(1)	D	$1.27	799,496	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	08/22/2025
	** 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.

FAQ

What did Sean Mackay report on the Form 4 for LAB?

The Form 4 reports a Code F disposition of 19,661 shares at $1.27 per share on 08/20/2025, withheld to satisfy tax obligations from vested RSUs.

Why were the 19,661 LAB shares disposed of?

The shares were withheld to satisfy tax withholding obligations arising from the vesting of restricted stock units granted on May 20, 2024 and March 21, 2025.

How many LAB shares does Sean Mackay own after the transaction?

Following the reported withholding, Mackay beneficially owns 799,496 shares, held directly.

What is the relationship of the reporting person to Standard BioTools (LAB)?

The reporting person is an officer (SVP & Chief Business Officer) and is also identified as a director.

Does this Form 4 indicate an open-market sale by the insider?

No. The filing indicates a withholding for taxes on vested RSUs rather than an open-market sale for cash generation.