Standard BioTools exec has 25.7K shares withheld

STANDARD BIOTOOLS INC.

Rhea-AI Filing Summary

STANDARD BIOTOOLS INC. (LAB) reported that executive Sean Mackay, SVP & Chief Business Officer, had 25,729 shares of common stock withheld on August 20, 2026 to satisfy tax withholding obligations arising from the vesting of previously granted restricted stock units. Following this tax-withholding disposition, he holds 1,480,823 shares of common stock directly.

Insider Trade Summary

Tax Withholding: 25,729 shares

Tax Withholding 1 txn

Insider Mackay Sean

Role SVP & Chief Business Officer

Type	Security	Shares	Price	Value
Tax Withholding	Common Stock F1	25,729	$0.672	$17K

Holdings After Transaction: Common Stock — 1,480,823 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 ("RSUs") granted to the reporting person on May 20, 2024, March 21, 2025 and March 20, 2026, which grants were originally reported on Form 3 and Form 4s filed with the U.S. Securities and Exchange Commission on September 3, 2024, March 24, 2025 and April 8, 2026.

Key Figures

Shares delivered/withheld for tax liability: 25,729 shares Per-share value for tax-withholding shares: $0.6720 per share Shares owned after transaction: 1,480,823 shares

3 metrics

Shares delivered/withheld for tax liability 25,729 shares Common Stock, code F tax-withholding disposition on August 20, 2026

Per-share value for tax-withholding shares $0.6720 per share Valuation applied to 25,729 withheld shares

Shares owned after transaction 1,480,823 shares Common Stock directly owned by Sean Mackay after August 20, 2026 transaction

Key Terms

restricted stock units, tax withholding obligations, Form 4s

3 terms

restricted stock units financial

"tax withholding obligations that arose upon the vesting of restricted stock units ("RSUs")"

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 obligations financial

"shares were withheld from the reporting person to satisfy the tax withholding obligations"

Form 4s regulatory

"which grants were originally reported on Form 3 and Form 4s filed"

Form 4s are regulatory filings that report changes in ownership of a company’s stock by insiders — such as executives, directors, or large shareholders — and must be filed shortly after they buy or sell shares. For investors, these filings are like a public receipt showing what people closest to the company are doing with their own money, offering a quick signal of insider confidence or concern that can inform trading decisions.

FAQ

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

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

Sean Mackay had 25,729 shares of STANDARD BIOTOOLS INC. common stock withheld on August 20, 2026 to satisfy tax withholding obligations from RSU vesting, a non-market disposition reported on Form 4.

Was the LAB Form 4 transaction a sale on the open market?

No. The Form 4 states the transaction used code F, describing payment of tax liability by delivering or withholding securities, and the footnote explains the 25,729 shares were withheld to satisfy tax withholding obligations from RSU vesting.

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

After the August 20, 2026 tax-withholding transaction, Sean Mackay directly holds 1,480,823 shares of STANDARD BIOTOOLS INC. common stock, as reported in the Form 4 filing.

What price per share was used for the LAB tax-withholding shares?

The 25,729 shares withheld for tax withholding obligations were valued at $0.6720 per share, according to the Form 4 transaction data for STANDARD BIOTOOLS INC. (LAB).

What awards triggered the tax withholding reported in the LAB Form 4?

The tax withholding arose from the vesting of restricted stock units (RSUs) granted to Sean Mackay on May 20, 2024, March 21, 2025, and March 20, 2026, as described in the Form 4 footnote.

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

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Available on EDGAR 08/24/2026 - 05:07 PM EDT Accepted by SEC EDGAR 08/24/2026 - 05:06 PM EDT 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 MASSACHUSETTS 02109

(City) (State) (Zip)

UNITED STATES

(Country)

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

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
08/20/2026

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)
			Code	V	Amount	(A) or (D)	Price
Common Stock	08/20/2026		F		25,729(1)	D	$0.672	1,480,823	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 ("RSUs") granted to the reporting person on May 20, 2024, March 21, 2025 and March 20, 2026, which grants were originally reported on Form 3 and Form 4s filed with the U.S. Securities and Exchange Commission on September 3, 2024, March 24, 2025 and April 8, 2026.

	/s/ Sean Mackay by Tomone Tanaka, Attorney-in-Fact	08/24/2026
	** 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.
* Form 4: SEC 1474 (03-26)