BillionToOne officer plans $3.9M stock sale

Officer Thomas P. Lynch files a Rule 144 notice to potentially sell 35,112 BillionToOne Class A shares after a prior 20,000-share sale.

Available on EDGAR 09/17/2026 - 04:21 PM EDT Accepted by SEC EDGAR 09/17/2026 - 04:20 PM EDT Learn about SEC filing dates

Rhea-AI Filing Summary

BillionToOne, Inc. (BLLN) has a notice of proposed sale under Rule 144 filed for officer Thomas P. Lynch. The notice covers the potential sale of 35,112 Class A shares, expected around September 17, 2026, through Fidelity Brokerage Services LLC, in connection with a stock option exercise for cash. The filing states an aggregate market value of $3,873,965.78 for these shares and notes that 42,644,388 Class A shares were outstanding, which is a baseline figure, not the amount being sold. Over the prior three months, Lynch sold 20,000 Class A shares on September 8, 2026 for $1,999,879.96.

Key Figures

Shares to be sold under Rule 144: 35,112 shares Aggregate market value of proposed sale: $3,873,965.78 Shares outstanding: 42,644,388 shares +2 more

5 metrics

Shares to be sold under Rule 144 35,112 shares Proposed Class A share sale for Thomas P. Lynch expected around September 17, 2026

Aggregate market value of proposed sale $3,873,965.78 Value of 35,112 Class A shares covered by Rule 144 notice

Shares outstanding 42,644,388 shares Class A shares outstanding for BillionToOne, Inc. as stated in the notice

Recent shares sold 20,000 shares Class A shares sold by Thomas P. Lynch on September 8, 2026

Proceeds from recent sale $1,999,879.96 Total received for 20,000 Class A shares sold on September 8, 2026

Key Terms

Rule 144, aggregate market value, stock option exercise, attorney-in-fact

4 terms

Rule 144 regulatory

"See the definition of "person" in paragraph (a) of Rule 144."

Rule 144 is a U.S. securities regulation that sets conditions under which restricted or insider-held shares can be legally resold to the public, such as required holding periods, availability of public information, limits on how much can be sold at once, and certain filing requirements. For investors it matters because it determines when previously locked-up shares can enter the market — like a release valve that can increase supply, affect share price, and signal insider intent.

aggregate market value financial

"Class A ... 35112 | 3873965.78 | 42644388 | 09/17/2026"

Aggregate market value is the combined price you would pay to buy all outstanding shares of a company or all companies in a group at current market prices — essentially the sum of each stock’s market capitalization. It matters to investors because it shows the overall size and weight of an investment or sector (like the total cost to buy every piece of a puzzle), helps compare scale across companies or markets, and influences index composition and risk exposure.

stock option exercise financial

"Class A | 09/17/2026 | Stock Option Exercise | Issuer"

A stock option exercise is the act of using a previously granted right to buy shares of a company's stock at a specific, predetermined price by paying that price and receiving the shares. It matters to investors because exercising changes who owns the shares (which can dilute existing ownership), can trigger taxable events and shift potential gains or losses, and affects voting power and the company’s outstanding share count—like turning a voucher into an actual product that becomes part of circulating supply.

attorney-in-fact regulatory

"as attorney-in-fact for Thomas Lynch"

An attorney-in-fact is the person or entity given legal authority through a power of attorney to act on behalf of another for specific tasks, such as signing documents, voting shares, or handling transactions. For investors, this matters because it lets a trusted representative make timely decisions or complete paperwork when the owner cannot, much like handing keys to someone to run errands on your behalf—so checks on scope and limits of that authority are important.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What does the Form 144 filing for BLLN disclose about planned share sales?

The notice discloses that officer Thomas P. Lynch may sell 35,112 Class A shares of BillionToOne, Inc., expected around September 17, 2026, in connection with a stock option exercise for cash through Fidelity Brokerage Services LLC.

What is the aggregate market value of the BLLN shares covered by this Form 144?

The Form 144 states an aggregate market value of $3,873,965.78 for the 35,112 Class A shares of BillionToOne, Inc. that are covered by the proposed Rule 144 sale.

How many BillionToOne (BLLN) shares has Thomas P. Lynch sold recently?

Over the prior three months, Thomas P. Lynch sold 20,000 Class A shares of BillionToOne, Inc. on September 8, 2026, for a total of $1,999,879.96, according to the Form 144 disclosure of past sales.

How many BillionToOne (BLLN) shares are outstanding according to the Form 144?

The Form 144 lists 42,644,388 Class A shares outstanding for BillionToOne, Inc. This figure provides context for the company’s equity base and is not the number of shares being proposed for sale.

On which market are the BLLN shares in this Form 144 listed?

The shares covered by the Form 144 are Class A common stock of BillionToOne, Inc. listed on NASDAQ, as identified in the securities information section of the notice.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Form 144 Filer Information	UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Form 144 NOTICE OF PROPOSED SALE OF SECURITIES PURSUANT TO RULE 144 UNDER THE SECURITIES ACT OF 1933
FORM 144

144: Filer Information

Filer CIK	0001659824
Filer CCC	XXXXXXXX
Is this a LIVE or TEST Filing?	LIVE TEST
Submission Contact Information
Name
Phone
E-Mail Address

144: Issuer Information

Name of Issuer	BillionToOne, Inc.
SEC File Number	001-42934
Address of Issuer	1035 O'BRIEN DRIVE MENLO PARK CALIFORNIA 94025
Phone	650-460-2551
Name of Person for Whose Account the Securities are To Be Sold	Lynch Thomas P.
See the definition of "person" in paragraph (a) of Rule 144. Information is to be given not only as to the person for whose account the securities are to be sold but also as to all other persons included in that definition. In addition, information shall be given as to sales by all persons whose sales are required by paragraph (e) of Rule 144 to be aggregated with sales for the account of the person filing this notice.
Relationship to Issuer	Officer

144: Securities Information

Title of the Class of Securities To Be Sold	Name and Address of the Broker	Number of Shares or Other Units To Be Sold	Aggregate Market Value	Number of Shares or Other Units Outstanding	Approximate Date of Sale	Name the Securities Exchange
Class A	Fidelity Brokerage Services LLC 900 Salem Street Smithfield RI 02917	35112	3873965.78	42644388	09/17/2026	NASDAQ

Furnish the following information with respect to the acquisition of the securities to be sold and with respect to the payment of all or any part of the purchase price or other consideration therefor:

144: Securities To Be Sold

Title of the Class	Date you Acquired	Nature of Acquisition Transaction	Name of Person from Whom Acquired	Is this a Gift?	Date Donor Acquired	Amount of Securities Acquired	Date of Payment	Nature of Payment *
Class A	09/17/2026	Stock Option Exercise	Issuer			35112	09/17/2026	Cash

* If the securities were purchased and full payment therefor was not made in cash at the time of purchase, explain in the table or in a note thereto the nature of the consideration given. If the consideration consisted of any note or other obligation, or if payment was made in installments describe the arrangement and state when the note or other obligation was discharged in full or the last installment paid.

Furnish the following information as to all securities of the issuer sold during the past 3 months by the person for whose account the securities are to be sold.

144: Securities Sold During The Past 3 Months

Name and Address of Seller	Title of Securities Sold	Date of Sale	Amount of Securities Sold	Gross Proceeds
Thomas P. Lynch 1035 O'Brien Drive Menlo Park CA 94025	Class A	09/08/2026	20000	1999879.96

144: Remarks and Signature

Remarks
Date of Notice	09/17/2026
Date of Plan Adoption or Giving of Instruction, If Relying on Rule 10b5-1	06/08/2026
ATTENTION:
The person for whose account the securities to which this notice relates are to be sold hereby represents by signing this notice that he does not know any material adverse information in regard to the current and prospective operations of the Issuer of the securities to be sold which has not been publicly disclosed. If such person has adopted a written trading plan or given trading instructions to satisfy Rule 10b5-1 under the Exchange Act, by signing the form and indicating the date that the plan was adopted or the instruction given, that person makes such representation as of the plan adoption or instruction date.
Signature	/s/ Daniel Tucci, as a duly authorized representative of Fidelity Brokerage Services LLC, as attorney-in-fact for Thomas Lynch
ATTENTION: Intentional misstatements or omission of facts constitute Federal Criminal Violations (See 18 U.S.C. 1001)