STOCK TITAN

Quanterix (QTRX) COO exercises 1,558 RSUs; 467 shares withheld for taxes

Filing Impact
(Neutral)
Filing Sentiment
(Neutral)
Form Type
4

Rhea-AI Filing Summary

Quanterix Corp Chief Operating Officer Michael Francis Miller exercised restricted stock units into common stock and had shares withheld to cover taxes. On April 15, 2026, he acquired a total of 1,558 shares of common stock through multiple RSU conversions, all at a stated price of $0.00 per share.

To satisfy tax obligations related to these vesting events, 467 shares of common stock were disposed of at $3.60 per share in tax-withholding transactions. Following these transactions, Miller directly held 32,522 shares of Quanterix common stock.

Positive

  • None.

Negative

  • None.
Insider Miller Michael Francis
Role Chief Operating Officer
Type Security Shares Price Value
Exercise Restricted Stock Unit 81 $0.00 --
Exercise Restricted Stock Unit 136 $0.00 --
Exercise Restricted Stock Unit 135 $0.00 --
Exercise Restricted Stock Unit 372 $0.00 --
Exercise Restricted Stock Unit 834 $0.00 --
Exercise Common Stock 81 $0.00 --
Tax Withholding Common Stock 25 $3.60 $90.00
Exercise Common Stock 136 $0.00 --
Tax Withholding Common Stock 41 $3.60 $147.60
Exercise Common Stock 135 $0.00 --
Tax Withholding Common Stock 41 $3.60 $147.60
Exercise Common Stock 372 $0.00 --
Tax Withholding Common Stock 111 $3.60 $399.60
Exercise Common Stock 834 $0.00 --
Tax Withholding Common Stock 249 $3.60 $896.40
Holdings After Transaction: Restricted Stock Unit — 841 shares (Direct); Common Stock — 31,512 shares (Direct)
Footnotes (1)
  1. Restricted stock units convert into common stock on a one-for-one basis. On February 6, 2023, the reporting person was granted 3,929 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 15th day of each month thereafter. On March 15, 2023, the reporting person was granted 6,566 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 15th day of each month thereafter. On February 2, 2024, the reporting person was granted 6,494 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 15th day of each month thereafter. On May 21, 2024, the reporting person was granted 17,878 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 15th day of each month thereafter. On February 4, 2025, the reporting person was granted 40,036 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 15th day of each month thereafter.
RSU shares exercised 1,558 shares Total exercise or conversion shares reported in transaction summary
Tax-withheld shares 467 shares Shares delivered to satisfy tax liability
Tax-withholding price $3.60 per share Price for F-code tax-withholding dispositions of common stock
Shares held after transactions 32,522 shares Total direct common stock ownership following all reported entries
Individual RSU conversion lot 834 units Largest single RSU tranche converted into common stock on April 15, 2026
RSU grant example 40,036 units Grant on February 4, 2025 with 25% cliff and 36 monthly vesting installments
Restricted stock units financial
"Restricted stock units convert into common stock on a one-for-one basis."
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 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.
Exercise or conversion of derivative security financial
"transaction_code_description: Exercise or conversion of derivative security"
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.
one-for-one basis financial
"Restricted stock units convert into common stock on a one-for-one basis."
SEC Form 4
FORM 4UNITED 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)
Director10% Owner
XOfficer (give title below)Other (specify below)
Chief Operating Officer
2a. Foreign Trading Symbol
3. Date of Earliest Transaction (Month/Day/Year)
04/15/2026
6. Individual or Joint/Group Filing (Check Applicable Line)
XForm 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)
CodeVAmount(A) or (D)Price
Common Stock04/15/2026M81A(1)31,512D
Common Stock04/15/2026F25D$3.631,487D
Common Stock04/15/2026M136A(1)31,623D
Common Stock04/15/2026F41D$3.631,582D
Common Stock04/15/2026M135A(1)31,717D
Common Stock04/15/2026F41D$3.631,676D
Common Stock04/15/2026M372A(1)32,048D
Common Stock04/15/2026F111D$3.631,937D
Common Stock04/15/2026M834A(1)32,771D
Common Stock04/15/2026F249D$3.632,522D
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)
CodeV(A)(D)Date ExercisableExpiration DateTitleAmount or Number of Shares
Restricted Stock Unit$0.0004/15/2026M81 (2) (2)Common Stock81$0.00841D
Restricted Stock Unit$0.0004/15/2026M136 (3) (3)Common Stock136$0.001,525D
Restricted Stock Unit$0.0004/15/2026M135 (4) (4)Common Stock135$0.002,981D
Restricted Stock Unit$0.0004/15/2026M372 (5) (5)Common Stock372$0.009,317D
Restricted Stock Unit$0.0004/15/2026M834 (6) (6)Common Stock834$0.0028,359D
Explanation of Responses:
1. Restricted stock units convert into common stock on a one-for-one basis.
2. On February 6, 2023, the reporting person was granted 3,929 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 15th day of each month thereafter.
3. On March 15, 2023, the reporting person was granted 6,566 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 15th day of each month thereafter.
4. On February 2, 2024, the reporting person was granted 6,494 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 15th day of each month thereafter.
5. On May 21, 2024, the reporting person was granted 17,878 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 15th day of each month thereafter.
6. On February 4, 2025, the reporting person was granted 40,036 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 15th day of each month thereafter.
Remarks:
/s/ Bonnie McManus, Attorney-in-Fact04/16/2026
** Signature of Reporting PersonDate
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 did Quanterix (QTRX) COO Michael Francis Miller report in this Form 4?

Michael Francis Miller reported multiple transactions where restricted stock units converted into Quanterix common stock and some shares were withheld for taxes. These events reflect equity compensation vesting, not open-market purchases or sales, and adjust his direct ownership position in the company.

How many Quanterix (QTRX) shares did the COO acquire through RSU exercises?

He acquired 1,558 shares of Quanterix common stock through the exercise or conversion of restricted stock units. The RSUs convert into common stock on a one-for-one basis, so each vested unit delivered one share to the executive’s direct holdings.

How many Quanterix (QTRX) shares were withheld for taxes and at what price?

A total of 467 shares of Quanterix common stock were disposed of in tax-withholding transactions at $3.60 per share. These F-code transactions pay required tax obligations and are not open-market sales initiated for investment reasons.

What is Michael Francis Miller’s Quanterix (QTRX) shareholding after these transactions?

After completing all RSU conversions and related tax-withholding dispositions, Michael Francis Miller directly holds 32,522 shares of Quanterix common stock. This figure reflects his updated ownership after both the share acquisitions and the shares delivered for tax payments.

How are the Quanterix (QTRX) RSU grants to the COO structured for vesting?

The RSU grants vest 25% on the first anniversary of the grant date, with the remaining 75% in 36 equal monthly installments on the 15th day of each following month. This schedule applies to multiple grants awarded between 2023 and 2025.

Are the Quanterix (QTRX) Form 4 transactions open-market buys or routine compensation events?

These transactions are routine compensation events, involving RSU conversions and tax-withholding dispositions. The filing shows no open-market purchases or sales; instead, it records equity awards vesting and associated tax payments using company stock.