Quantum-Si (QSI) CFO’s 8,655-share sale tied to RSU tax withholding

Rhea-AI Filing Summary

Quantum-Si Inc Chief Financial Officer Jeffry R. Keyes reported routine tax-related stock sales. He sold a total of 8,655 shares of Class A Common Stock in open-market transactions on March 20 and March 23 at weighted average prices around $0.83 per share.

According to the footnotes, these sales were made under a mandatory Quantum-Si sell-to-cover provision to satisfy federal, state and local withholding taxes tied to the vesting of previously granted restricted stock units. After these transactions, he continued to hold 1,807,345 shares directly.

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

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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^*

Keyes Jeffry R.

(Last) (First) (Middle)

C/O QUANTUM-SI INCORPORATED

29 BUSINESS PARK DRIVE

(Street)

BRANFORD CONNECTICUT 06405

(City) (State) (Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
Quantum-Si Inc [ QSI ]

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

	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	Chief Financial Officer

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
03/20/2026

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
Class A Common Stock	03/20/2026		S(1)		4,233	D	$0.8483(2)	1,811,767	D
Class A Common Stock	03/23/2026		S(1)		4,422	D	$0.8266(3)	1,807,345	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. Represents shares sold pursuant to a mandatory Quantum-Si sell-to-cover provision for required federal, state and local withholding taxes in connection with the vesting of previously granted restricted stock units. Individual is not able to alter this mandatory sell-to-cover provision that is enacted at the grant date of the related restricted stock unit award.

2. Represents the weighted average sales price per share. The shares sold at prices ranging from $0.8314 to $0.8718 per share. Full information regarding the number of shares sold at each price shall be provided upon request to the staff of the U.S. Securities and Exchange Commission, the Issuer, or a security holder of the Issuer.

3. Represents the weighted average sales price per share. The shares sold at prices ranging from $0.7973 to $0.8525 per share. Full information regarding the number of shares sold at each price shall be provided upon request to the staff of the U.S. Securities and Exchange Commission, the Issuer, or a security holder of the Issuer.

	/s/ Christian LaPointe, Ph.D., Attorney-in-Fact.	03/24/2026
	** 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)

FAQ

What insider transaction did Quantum-Si (QSI) report for its CFO?

Quantum-Si reported that CFO Jeffry R. Keyes sold 8,655 shares of Class A Common Stock. The sales on March 20 and March 23 were tied to required tax withholding from the vesting of previously granted restricted stock units under a mandatory sell-to-cover provision.

At what prices did the Quantum-Si (QSI) CFO’s shares sell in this Form 4?

The reported shares sold at weighted average prices around $0.83 per share. Footnotes state prices ranged from $0.8314 to $0.8718 on one date and from $0.7973 to $0.8525 on the other, with full breakdowns available on request.

Why did Quantum-Si (QSI) CFO Jeffry Keyes sell shares in this filing?

The sales were executed under a mandatory Quantum-Si sell-to-cover provision to pay required federal, state and local withholding taxes. These obligations arose from the vesting of previously granted restricted stock units, so the transactions were mechanistic rather than discretionary portfolio decisions.

How many Quantum-Si (QSI) shares does the CFO hold after these transactions?

After completing the tax-related sales, CFO Jeffry R. Keyes directly held 1,807,345 shares of Quantum-Si Class A Common Stock. This shows the 8,655 shares sold represent a small portion of his overall reported ownership position following the Form 4 transactions.

Were the Quantum-Si (QSI) CFO’s stock sales open-market or part of a plan?

The Form 4 classifies the transactions as open-market sales, but footnotes clarify they followed a mandatory sell-to-cover provision set at each RSU grant date. He could not alter this requirement, indicating the timing was driven by tax obligations on vesting.