Standard Biotools SVP shares withheld for taxes

STANDARD BIOTOOLS INC. senior vice president and chief business officer Sean Mackay reported a routine tax-withholding transaction.

Rhea-AI Filing Summary

STANDARD BIOTOOLS INC. senior vice president and chief business officer Sean Mackay reported a routine tax-withholding transaction. On May 20, 2026, 25,729 shares of common stock were withheld to satisfy tax obligations arising from vested restricted stock units granted on May 20, 2024, March 21, 2025 and March 20, 2026.

Following this withholding, Mackay directly holds 1,006,552 shares of common stock. This Form 4 reflects compensation-related tax settlement rather than an open-market purchase or sale.

Insider Trade Summary

Exercise Price or Tax Liability: 25,729 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	25,729	$1.00	$26K

Holdings After Transaction: Common Stock — 1,006,552 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, 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, respectively.

Key Figures

Shares withheld for taxes: 25,729 shares Withholding price per share: $1.00 per share Shares held after transaction: 1,006,552 shares +1 more

4 metrics

Shares withheld for taxes 25,729 shares Tax-withholding disposition on May 20, 2026

Withholding price per share $1.00 per share Recorded transaction price for withheld shares

Shares held after transaction 1,006,552 shares Direct common stock holdings following withholding

Tax-withholding share count 25,729 shares Also reported as taxWithholdingShares in summary data

Key Terms

restricted stock units, tax withholding obligations, Form 4, common stock

4 terms

restricted stock units financial

"upon the vesting of restricted stock units granted to the reporting person"

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

"withheld from the reporting person to satisfy the tax withholding obligations that arose"

Form 4 regulatory

"originally reported on Form 3 and Form 4s filed with the U.S. Securities and Exchange Commission"

Form 4 is a official document that company insiders, such as executives or major shareholders, file with regulators whenever they buy or sell company shares. It provides transparency about how those with inside knowledge are trading, helping investors see if insiders are confident in the company's prospects or may be selling for personal reasons. This information can influence investor decisions by revealing insiders' perspectives on the company's value.

common stock financial

"security_title": "Common Stock""

Common stock represents ownership shares in a company, giving investors a stake in its success and a say in important decisions through voting rights. It is the most common type of stock traded on markets and can provide income through dividends, as well as potential for value growth. For investors, holding common stock means sharing in the company’s profits and risks.

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 Sean Mackay had 25,729 common shares withheld to cover tax obligations. The withholding occurred on May 20, 2026 and related to the vesting of previously granted restricted stock units, making this a compensation-driven tax settlement, not an open-market trade.

How many STANDARD BIOTOOLS (LAB) shares were withheld for Sean Mackay’s taxes?

A total of 25,729 STANDARD BIOTOOLS common shares were withheld to satisfy Sean Mackay’s tax obligations. The withholding price was recorded at $1.00 per share and tied to the vesting of restricted stock units granted in 2024, 2025 and 2026.

How many STANDARD BIOTOOLS (LAB) shares does Sean Mackay hold after this Form 4?

After the tax-withholding transaction, Sean Mackay directly holds 1,006,552 STANDARD BIOTOOLS common shares. This figure reflects his post-transaction position and shows that the withheld 25,729 shares represent a relatively small portion of his overall direct holdings.

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

The tax-withholding disposition arose from the vesting of restricted stock units previously granted to Sean Mackay. These RSU grants were made on May 20, 2024, March 21, 2025 and March 20, 2026, and the company withheld shares to pay associated tax liabilities.

Does this STANDARD BIOTOOLS (LAB) Form 4 indicate an open-market sale by Sean Mackay?

This Form 4 does not indicate an open-market sale by Sean Mackay. Instead, it records shares withheld by the company to satisfy tax obligations on RSU vesting, a common compensation-related mechanism distinct from discretionary buying or selling in the market.

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

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Accepted by SEC EDGAR 05/22/2026 - 05:17 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 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)
05/20/2026

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	05/20/2026		F		25,729(1)	D	$1	1,006,552	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, 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, respectively.

	/s/ Sean Mackay by Tomone Tanaka, Attorney-in-Fact	05/22/2026
	** 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)