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Quanterix (QTRX) CFO reports RSU vesting and tax-withholding share dispositions

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

Rhea-AI Filing Summary

Quanterix Corp Chief Financial Officer Vandana Sriram reported routine equity compensation activity involving restricted stock units (RSUs). On May 15, 2026, RSUs converted into common stock in several tranches, including 1,056, 514, and 263 shares, reflecting scheduled vesting.

To cover tax obligations, the filing shows share dispositions of 315, 154, and 79 shares of common stock at $2.75 per share, characterized as tax-withholding transactions rather than open-market sales. Following these transactions, the CFO directly held 28,897 shares of Quanterix common stock, while additional RSUs remain outstanding and continue to vest over time.

Positive

  • None.

Negative

  • None.
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 79 $2.75 $217.25
Exercise Common Stock 514 $0.00 --
Tax Withholding Common Stock 154 $2.75 $423.50
Exercise Common Stock 1,056 $0.00 --
Tax Withholding Common Stock 315 $2.75 $866.25
Holdings After Transaction: Restricted Stock Unit — 3,945 shares (Direct, null); Common Stock — 28,976 shares (Direct, null)
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 36 equal monthly installments on the 15th day of each month 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 36 equal monthly installments on the 15th day of each month 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 36 equal monthly installments on the 15th day of each month thereafter.
Tax-withholding shares 315 shares Common stock disposed at $2.75 on May 15, 2026
Additional tax-withholding shares 154 shares Common stock disposed at $2.75 on May 15, 2026
Further tax-withholding shares 79 shares Common stock disposed at $2.75 on May 15, 2026
RSU conversion tranche 1,056 shares Common stock acquired via RSU conversion on May 15, 2026
RSU conversion tranche 514 shares Common stock acquired via RSU conversion on May 15, 2026
RSU conversion tranche 263 shares Common stock acquired via RSU conversion on May 15, 2026
Common shares held after transactions 28,897 shares Direct ownership after May 15, 2026 transactions
Tax-withholding total 548 shares Total shares used for tax obligations per summary
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.
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*
Sriram Vandana

(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 Financial 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 Stock05/15/2026M263A(1)28,976D
Common Stock05/15/2026F79D$2.7528,897D
Common Stock05/15/2026M514A(1)29,411D
Common Stock05/15/2026F154D$2.7529,257D
Common Stock05/15/2026M1,056A(1)30,313D
Common Stock05/15/2026F315D$2.7529,998D
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$0.0005/15/2026M263 (2) (2)Common Stock263$0.003,945D
Restricted Stock Unit$0.0005/15/2026M514 (3) (3)Common Stock514$0.0010,797D
Restricted Stock Unit$0.0005/15/2026M1,056 (4) (4)Common Stock1,056$0.0034,866D
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 36 equal monthly installments on the 15th day of each month 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 36 equal monthly installments on the 15th day of each month 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 36 equal monthly installments on the 15th day of each month thereafter.
Remarks:
/s/ Bonnie McManus, as 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 did Quanterix (QTRX) CFO Vandana Sriram report in this Form 4?

The Form 4 reports routine equity compensation activity for the CFO. Restricted stock units vested and converted into common stock, and some shares were withheld to cover tax liabilities associated with those vestings, rather than being sold in the open market.

How many Quanterix (QTRX) shares did the CFO acquire through RSU vesting?

The CFO acquired common stock through RSU conversions in multiple tranches of 1,056, 514, and 263 shares. These transactions reflect scheduled vesting of restricted stock units granted under prior equity awards, converting on a one-for-one basis into Quanterix common shares.

Were any of the Quanterix (QTRX) CFO’s transactions open-market sales?

The filing classifies the dispositions as tax-withholding transactions, not open-market sales. Shares totaling 315, 154, and 79 were delivered at $2.75 per share to satisfy tax obligations arising from RSU vesting, rather than representing discretionary stock sales.

How many Quanterix (QTRX) shares does the CFO hold after these transactions?

After the reported transactions, the CFO directly holds 28,897 shares of Quanterix common stock. This figure reflects net ownership following RSU conversions into common stock and the related share dispositions used to satisfy tax liabilities on the vesting events.

What do the Quanterix (QTRX) RSU grants in the footnotes indicate?

The footnotes describe RSU grants on August 21, 2023, February 2, 2024, and February 4, 2025. Each grant vests 25% on the first anniversary of the grant date, with the remaining 75% vesting in 36 equal monthly installments, creating ongoing equity vesting over several years.

How do Quanterix (QTRX) restricted stock units convert into shares?

The filing states that restricted stock units convert into common stock on a one-for-one basis. As RSUs vest according to their schedules, each unit automatically delivers one share of Quanterix common stock to the holder, subject to applicable tax-withholding transactions.