STOCK TITAN

Quanterix (QTRX) CTO gains 1,558 shares from RSU vesting, 467 withheld for tax

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

Rhea-AI Filing Summary

Quanterix Corp Chief Technology Officer Michael Francis Miller reported routine equity compensation activity. On May 15, 2026, restricted stock units vested and were converted into 1,558 shares of Common Stock, while 467 shares were withheld at $2.75 per share to cover tax obligations. After these transactions, he directly owned 32,694 Common shares and 760 restricted stock units that may vest later.

Positive

  • None.

Negative

  • None.
Insider Miller Michael Francis
Role Chief Technology 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 $2.75 $68.75
Exercise Common Stock 136 $0.00 --
Tax Withholding Common Stock 41 $2.75 $112.75
Exercise Common Stock 135 $0.00 --
Tax Withholding Common Stock 41 $2.75 $112.75
Exercise Common Stock 372 $0.00 --
Tax Withholding Common Stock 111 $2.75 $305.25
Exercise Common Stock 834 $0.00 --
Tax Withholding Common Stock 249 $2.75 $684.75
Holdings After Transaction: Restricted Stock Unit — 760 shares (Direct, null); Common Stock — 32,694 shares (Direct, null)
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.
Shares acquired via RSU vesting 1,558 shares Restricted stock units converted into Common Stock on May 15, 2026
Shares withheld for taxes 467 shares Tax-withholding dispositions at $2.75 per share on May 15, 2026
Post-transaction Common Stock holdings 32,694 shares Direct ownership after reported transactions
Remaining restricted stock units 760 RSUs Derivative holdings after conversions reported on May 15, 2026
Tax-withholding price $2.75 per share Price used for F-code tax-withholding dispositions
Total derivative exercises 1,558 shares Exercise or conversion of derivative securities per transactionSummary
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.
derivative security financial
"Exercise or conversion of derivative security"
A derivative security is a financial contract whose value comes from the price or performance of something else, such as a stock, bond, commodity, or market index. For investors it acts like an insurance policy or a wager: it can be used to protect against losses, lock in prices, or amplify gains and losses, so it can change a portfolio’s risk and potential return without owning the underlying asset directly.
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.
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 Technology Officer
2a. Foreign Trading Symbol
3. Date of Earliest Transaction (Month/Day/Year)
05/15/2026
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 Stock05/15/2026M81A(1)32,694D
Common Stock05/15/2026F25D$2.7532,669D
Common Stock05/15/2026M136A(1)32,805D
Common Stock05/15/2026F41D$2.7532,764D
Common Stock05/15/2026M135A(1)32,899D
Common Stock05/15/2026F41D$2.7532,858D
Common Stock05/15/2026M372A(1)33,230D
Common Stock05/15/2026F111D$2.7533,119D
Common Stock05/15/2026M834A(1)33,953D
Common Stock05/15/2026F249D$2.7533,704D
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$0.0005/15/2026M81 (2) (2)Common Stock81$0.00760D
Restricted Stock Unit$0.0005/15/2026M136 (3) (3)Common Stock136$0.001,389D
Restricted Stock Unit$0.0005/15/2026M135 (4) (4)Common Stock135$0.002,846D
Restricted Stock Unit$0.0005/15/2026M372 (5) (5)Common Stock372$0.008,945D
Restricted Stock Unit$0.0005/15/2026M834 (6) (6)Common Stock834$0.0027,525D
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-Fact05/18/2026
** 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 insider transactions did Quanterix (QTRX) report for Michael Francis Miller?

Quanterix reported that CTO Michael Francis Miller had restricted stock units vest into common shares and some shares withheld for taxes. These are compensation-related events, not open-market stock purchases or sales, and reflect ongoing equity grants rather than a change in investment stance.

How many Quanterix (QTRX) shares did the CTO acquire in this Form 4?

The CTO acquired 1,558 shares of Quanterix Common Stock through the vesting and conversion of restricted stock units. These shares came from previously granted equity awards, not market purchases, and represent part of his long-term compensation package linked to prior grant agreements.

How many Quanterix (QTRX) shares were withheld for taxes in this filing?

A total of 467 Quanterix Common shares were withheld to satisfy tax obligations, at a reported price of $2.75 per share. This tax-withholding disposition is a standard mechanism and does not represent an open-market sale by the executive to third-party investors.

What are Michael Francis Miller’s Quanterix (QTRX) holdings after these transactions?

Following the reported activity, Michael Francis Miller directly held 32,694 shares of Quanterix Common Stock and 760 restricted stock units. The remaining restricted stock units can convert into additional shares over time, subject to their specified vesting schedules and continued service conditions.

What do the restricted stock unit grants mean for Quanterix (QTRX) insiders?

The filing notes multiple restricted stock unit grants to the CTO, each vesting 25% after one year, then the rest in 36 monthly installments. This structure gradually delivers equity, aligning the executive’s compensation with Quanterix’s long-term performance and his continued employment at the company.

Were any Quanterix (QTRX) shares sold on the open market in this Form 4?

No open-market sales are indicated in this Form 4. The dispositions labeled with code F represent shares withheld to cover tax liabilities related to vesting, rather than discretionary sales into the market, and are a routine part of equity compensation administration.