Quanterix (QTRX) COO logs RSU conversion and small tax share disposal

Rhea-AI Filing Summary

Quanterix Corp Chief Operating Officer Michael Francis Miller reported routine equity compensation activity. He exercised 130 restricted stock units that converted into 130 shares of common stock on a one-for-one basis. To cover tax obligations, 39 common shares were disposed of through a tax-withholding transaction, not an open-market sale.

Following these transactions, Miller directly holds 32,613 shares of common stock and 549 restricted stock units that remain outstanding from a prior grant of 6,278 RSUs made on September 23, 2022.

Insider Trade Summary

130 shares exercised/converted

Mixed 3 txns

Insider Miller Michael Francis

Role Chief Operating Officer

Type	Security	Shares	Price	Value
Exercise	Restricted Stock Unit	130	$0.00	--
Exercise	Common Stock	130	$0.00	--
Tax Withholding	Common Stock	39	$3.13	$122.07

Holdings After Transaction: Restricted Stock Unit — 549 shares (Direct, null); Common Stock — 32,652 shares (Direct, null)

Footnotes (1)

1. Restricted stock units convert into common stock on a one-for-one basis. 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 converted: 130 units Shares withheld for taxes: 39 shares Common shares after transaction: 32,613 shares +3 more

6 metrics

RSUs converted 130 units Restricted stock units converting one-for-one into common stock on exercise date

Shares withheld for taxes 39 shares Tax-withholding disposition related to equity compensation event

Common shares after transaction 32,613 shares Direct holdings following reported Form 4 transactions

Outstanding RSUs after transaction 549 units Remaining from 6,278-unit RSU grant dated September 23, 2022

Original RSU grant size 6,278 units Grant to COO on September 23, 2022 with time-based vesting

Tax-withholding price $3.13 per share Value used for 39-share tax-withholding disposition

Key Terms

Restricted stock units, tax-withholding disposition, derivative security, vesting

4 terms

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

"transaction_action": "tax-withholding disposition""

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

"transaction_code_description": "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.

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^*

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)
04/30/2026

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)
			Code	V	Amount	(A) or (D)	Price
Common Stock	04/30/2026		M		130	A	(1)	32,652	D
Common Stock	04/30/2026		F		39	D	$3.13	32,613	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	04/30/2026		M			130	(2)	(2)	Common Stock	130	$0.00	549	D

Explanation of Responses:

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

2. 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	04/30/2026
	** 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)

FAQ

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

Michael Miller reported exercising 130 restricted stock units into common shares and a related tax-withholding disposition of 39 shares. These actions reflect routine equity compensation events rather than open-market buying or selling of Quanterix stock.

Did the Quanterix (QTRX) COO sell shares on the open market in this Form 4?

No open-market sale is reported. The Form 4 shows 39 shares disposed of solely to satisfy tax obligations tied to vesting, a tax-withholding disposition rather than a voluntary market sale decision by the Quanterix Chief Operating Officer.

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

After the reported transactions, Michael Miller directly holds 32,613 shares of Quanterix common stock. He also retains 549 outstanding restricted stock units from an earlier 6,278-unit grant that continues to vest according to its original schedule.

What restricted stock unit activity is disclosed for Quanterix (QTRX) in this filing?

The filing shows 130 restricted stock units converting into 130 common shares on a one-for-one basis. These RSUs are part of a 6,278-unit grant dated September 23, 2022, which vests over time according to a specified vesting schedule.

Is the Quanterix (QTRX) COO’s Form 4 transaction a strong bullish or bearish signal?

The reported activity appears routine. It reflects equity compensation vesting, an RSU-to-share conversion, and 39 shares withheld for taxes. Such compensation-related and tax-withholding transactions typically carry limited signaling value about management’s view of Quanterix stock.