Quanterix (QTRX) COO gains stock via RSU vesting with tax withholding

Filing Impact

(Neutral)

Filing Sentiment

(Neutral)

Form Type

Rhea-AI Filing Summary

Quanterix Corp Chief Operating Officer Michael Francis Miller exercised restricted stock units into common shares and had a portion withheld for taxes. On March 31, 2026, he converted 229 restricted stock units, which convert to common stock on a one-for-one basis, into the same number of common shares at a stated price of $0.00 per share.

To cover tax obligations, 69 common shares were disposed of through tax-withholding transactions at $3.52 per share, leaving him with a net increase of 160 common shares. Following these transactions, Miller directly owned 31,431 shares of Quanterix common stock. The restricted stock units exercised were part of prior grants from April 7, 2022 and September 23, 2022 that vest over time.

Insider Trade Summary

229 shares exercised/converted

Mixed 6 txns

Insider Miller Michael Francis

Role Chief Operating Officer

Type	Security	Shares	Price	Value
Exercise	Restricted Stock Unit	99	$0.00	--
Exercise	Restricted Stock Unit	130	$0.00	--
Exercise	Common Stock	99	$0.00	--
Tax Withholding	Common Stock	30	$3.52	$105.60
Exercise	Common Stock	130	$0.00	--
Tax Withholding	Common Stock	39	$3.52	$137.28

Holdings After Transaction: Restricted Stock Unit — 0 shares (Direct); Common Stock — 31,370 shares (Direct)

Footnotes (1)

Restricted stock units convert into common stock on a one-for-one basis. On April 7, 2022, the reporting person was granted 4,518 restricted stock units, vesting 25% on the first anniversary of the grant date, with the remaining 75% vesting in 36 equal monthly installments on the last day of each month thereafter. On September 23, 2022, the reporting person was granted 6,278 restricted stock units, vesting 25% on the first anniversary of the grant date, with the remaining 75% vesting in 36 equal monthly installments on the last day of each month thereafter.

Key Figures

RSUs exercised: 229 shares Tax-withheld shares: 69 shares Tax-withholding price: $3.52/share +3 more

6 metrics

RSUs exercised 229 shares Restricted stock units converted to common stock on March 31, 2026

Tax-withheld shares 69 shares Common shares delivered for tax liabilities at $3.52 per share

Tax-withholding price $3.52/share Value applied to 30 and 39 common shares for tax withholding

Post-transaction holdings 31,431 shares Common stock directly owned after March 31, 2026 transactions

April 7, 2022 RSU grant 4,518 units Vests 25% after one year, then 36 equal monthly installments

September 23, 2022 RSU grant 6,278 units Vests 25% after one year, then 36 equal monthly installments

Key Terms

Restricted Stock Unit, tax-withholding disposition, vesting

3 terms

Restricted Stock Unit financial

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

A restricted stock unit is a promise from a company to give an employee shares of stock after certain conditions are met, like staying with the company for a set amount of time. It’s like earning a bonus that turns into company stock once you’ve proven your commitment, making it a way to motivate and reward employees.

tax-withholding disposition financial

"Payment of exercise price or tax liability by delivering securities."

A tax-withholding disposition is an event or transaction—such as selling or transferring securities, exercising options, or receiving compensation—that triggers a requirement to hold back part of the payment and remit it to tax authorities. It matters to investors because it reduces the cash they receive immediately and can change the timing and amount of taxable income, like a cashier taking a portion of your sale proceeds to pay taxes before you get the rest.

vesting financial

"vesting 25% on the first anniversary of the grant date, with the remaining 75% vesting in 36 equal monthly installments"

Vesting is the process by which you earn full ownership of something, like company stock or a retirement benefit, over time. It’s like earning the right to keep a gift piece by piece the longer you stay with a company, making sure employees stay committed before they receive all the benefits.

Form 4 Insider Transactions: What Each Field Means →

04/02/2026 - 07:26 PM

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^*

Miller Michael Francis

(Last)

(First)

(Middle)

C/O QUANTERIX CORPORATION

900 MIDDLESEX TURNPIKE

(Street)

BILLERICA

MASSACHUSETTS

01821

(City)

(State)

(Zip)

UNITED STATES

(Country)

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 Operating Officer

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
03/31/2026

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)
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	Amount	(A) or (D)	Price		6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
Common Stock	03/31/2026		M		99	A	⁽¹⁾	31,370	D
Common Stock	03/31/2026		F		30	D	$3.52	31,340	D
Common Stock	03/31/2026		M		130	A	⁽¹⁾	31,470	D
Common Stock	03/31/2026		F		39	D	$3.52	31,431	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)
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)	Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	8. Price of Derivative Security (Instr. 5)		10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
Restricted Stock Unit	$0.00	03/31/2026		M			99	⁽²⁾	⁽²⁾	Common Stock	99	$0.00	0.00	D
Restricted Stock Unit	$0.00	03/31/2026		M			130	⁽³⁾	⁽³⁾	Common Stock	130	$0.00	679	D

Explanation of Responses:

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

2. On April 7, 2022, the reporting person was granted 4,518 restricted stock units, vesting 25% on the first anniversary of the grant date, with the remaining 75% vesting in 36 equal monthly installments on the last day of each month thereafter.

3. On September 23, 2022, the reporting person was granted 6,278 restricted stock units, vesting 25% on the first anniversary of the grant date, with the remaining 75% vesting in 36 equal monthly installments on the last day of each month thereafter.

Remarks:

	/s/ Bonnie McManus, Attorney-in-Fact	03/31/2026
	** 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)

Source: View Original Filing on SEC EDGAR

FAQ

What insider transaction did Quanterix (QTRX) COO Michael Miller report?

Michael Miller exercised 229 restricted stock units into common shares and had 69 shares withheld for taxes. These transactions increased his direct Quanterix common stock holdings while satisfying associated tax obligations through share delivery at $3.52 per share.

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

After the reported transactions, Michael Miller directly holds 31,431 shares of Quanterix common stock. This figure reflects both the 229 shares received from restricted stock unit exercises and the 69 shares disposed of to cover tax liabilities through share withholding.

Were Michael Miller’s Quanterix (QTRX) transactions open-market buys or routine vesting?

The transactions reflect routine equity compensation events, not open-market purchases. Miller exercised restricted stock units at a stated price of $0.00 per share, then disposed of 69 shares via tax-withholding to satisfy obligations, a common mechanism for handling taxes on vesting.

What price was used for the Quanterix (QTRX) tax-withholding shares?

The 69 shares withheld for taxes were valued at $3.52 per share. This price applies to both tax-withholding transactions reported, where 30 and 39 common shares were delivered to cover tax liabilities related to the restricted stock unit conversions.

What are the vesting terms of the Quanterix (QTRX) RSU grants to the COO?

Miller received 4,518 restricted stock units on April 7, 2022 and 6,278 on September 23, 2022, each vesting 25% on the first anniversary. The remaining 75% of each grant vests in 36 equal monthly installments on the last day of each month thereafter.