Quanterix (QTRX) CFO nets common shares from RSU vesting and tax withholding

Rhea-AI Filing Summary

Quanterix Corp Chief Financial Officer Vandana Sriram reported routine equity compensation activity involving restricted stock units that convert into common stock on a one-for-one basis. On March 15, 2026, she exercised RSUs covering 1,833 common shares in total through derivative exercises.

To satisfy tax obligations, 645 common shares were withheld and disposed of at $4.72 per share, with the remaining shares added to her direct holdings. Following these transactions, she directly owned 27,428 shares of Quanterix common stock. The RSUs stem from prior grants of 12,624 units on August 21, 2023, 24,675 units on February 2, 2024, and 50,712 units on February 4, 2025, each vesting over time with an initial 25% cliff and subsequent monthly installments.

Insider Trade Summary

1,833 shares exercised/converted

Mixed 9 txns

Insider Sriram Vandana

Role Chief Financial Officer

Type	Security	Shares	Price	Value
Exercise	Restricted Stock Unit	263	$0.00	--
Exercise	Restricted Stock Unit	514	$0.00	--
Exercise	Restricted Stock Unit	1,056	$0.00	--
Exercise	Common Stock	263	$0.00	--
Tax Withholding	Common Stock	93	$4.72	$438.96
Exercise	Common Stock	514	$0.00	--
Tax Withholding	Common Stock	181	$4.72	$854.32
Exercise	Common Stock	1,056	$0.00	--
Tax Withholding	Common Stock	371	$4.72	$2K

Holdings After Transaction: Restricted Stock Unit — 4,471 shares (Direct); Common Stock — 26,503 shares (Direct)

Footnotes (1)

1. Restricted stock units convert into common stock on a one-for-one basis. On August 21, 2023, the reporting person was granted 12,624 restricted stock units, vesting 25% on the first anniversary of the grant date, with the remaining 75% vesting in equal monthly installments of 6.25% on the monthly anniversary of the grant date thereafter. On February 2, 2024, the reporting person was granted 24,675 restricted stock units, vesting 25% on the first anniversary of the grant date, with the remaining 75% vesting in equal monthly installments of 6.25% on the monthly anniversary of the grant date thereafter. On February 4, 2025, the reporting person was granted 50,712 restricted stock units, vesting 25% on the first anniversary of the grant date, with the remaining 75% vesting in equal monthly installments of 6.25% on the monthly anniversary of the grant date thereafter.

Form 4 Insider Transactions: What Each Field Means →

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^*

Sriram Vandana

(Last) (First) (Middle)

C/O QUANTERIX CORPORATION

900 MIDDLESEX TURNPIKE

(Street)

BILLERICA MA 01821

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
Quanterix Corp [ QTRX ]

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

3. Date of Earliest Transaction (Month/Day/Year)
03/15/2026

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	03/15/2026		M		263	A	(1)	26,503	D
Common Stock	03/15/2026		F		93	D	$4.72	26,410	D
Common Stock	03/15/2026		M		514	A	(1)	26,924	D
Common Stock	03/15/2026		F		181	D	$4.72	26,743	D
Common Stock	03/15/2026		M		1,056	A	(1)	27,799	D
Common Stock	03/15/2026		F		371	D	$4.72	27,428	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
Restricted Stock Unit	$0.00	03/15/2026		M			263	(2)	(2)	Common Stock	263	$0.00	4,471	D
Restricted Stock Unit	$0.00	03/15/2026		M			514	(3)	(3)	Common Stock	514	$0.00	11,825	D
Restricted Stock Unit	$0.00	03/15/2026		M			1,056	(4)	(4)	Common Stock	1,056	$0.00	36,978	D

Explanation of Responses:

1. Restricted stock units convert into common stock on a one-for-one basis.

2. On August 21, 2023, the reporting person was granted 12,624 restricted stock units, vesting 25% on the first anniversary of the grant date, with the remaining 75% vesting in equal monthly installments of 6.25% on the monthly anniversary of the grant date thereafter.

3. On February 2, 2024, the reporting person was granted 24,675 restricted stock units, vesting 25% on the first anniversary of the grant date, with the remaining 75% vesting in equal monthly installments of 6.25% on the monthly anniversary of the grant date thereafter.

4. On February 4, 2025, the reporting person was granted 50,712 restricted stock units, vesting 25% on the first anniversary of the grant date, with the remaining 75% vesting in equal monthly installments of 6.25% on the monthly anniversary of the grant date thereafter.

Remarks:

	/s/ Bonnie McManus, as Attorney-in-Fact	03/16/2026
	** 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.

FAQ

What insider transaction did Quanterix (QTRX) report for CFO Vandana Sriram?

Quanterix reported its CFO exercised restricted stock units into common stock and had shares withheld for taxes. On March 15, 2026, she converted RSUs into 1,833 common shares and used 645 shares, priced at $4.72, to satisfy tax obligations.

How many Quanterix (QTRX) shares does the CFO hold after this Form 4 filing?

After the reported transactions, the CFO directly holds 27,428 Quanterix common shares. This reflects RSU conversions and share withholding for taxes on March 15, 2026, and represents her updated direct ownership position disclosed in the Form 4.

Were the Quanterix (QTRX) CFO’s transactions open-market buys or RSU-related?

The transactions were RSU-related, not open-market purchases or sales. The CFO exercised restricted stock units that automatically convert one-for-one into common stock and then delivered some of the resulting shares to cover associated tax liabilities.

What RSU grants underpin the Quanterix (QTRX) CFO’s March 2026 transactions?

The activity relates to RSU grants of 12,624 units on August 21, 2023, 24,675 units on February 2, 2024, and 50,712 units on February 4, 2025. Each grant vests 25% after one year, then 6.25% monthly thereafter.

At what price were Quanterix (QTRX) shares withheld for the CFO’s taxes?

Shares were withheld at a price of $4.72 per share to satisfy tax liabilities. In total, 645 common shares were delivered for taxes in several entries, all tied to the March 15, 2026 RSU conversions into common stock.

Does the Quanterix (QTRX) Form 4 show any discretionary stock sales by the CFO?

The Form 4 shows no open-market sales by the CFO. Dispositions reported under code F solely reflect shares delivered to pay tax liabilities arising from restricted stock unit conversions into common stock, rather than discretionary selling decisions.