BillionToOne’s Oguzhan Atay plans $2.5M stock sale

Rule 144 notice for BillionToOne, Inc. covers a planned sale of 24,999 Class A shares by insider-related accounts following several recent insider and related-party sales.

Rhea-AI Filing Summary

BillionToOne, Inc. (BLLN) is the issuer for a Rule 144 notice filed for the account of Oguzhan Atay covering potential sales of up to 24,999 Class A shares of common stock. The shares are to be sold through Fidelity Brokerage Services LLC on NASDAQ, in connection with a stock option exercise dated September 14, 2026.

The notice also reports that, within the prior three months, related accounts sold multiple blocks of BillionToOne Class A shares, including 26,250 shares by Oguzhan Atay on July 6, 2026, 32,500 shares by him on August 3, 2026, and 15,539 shares on August 5, 2026, as well as sales by his spouse and the Atay 2021 Dynasty Trust. Reported outstanding Class A shares total 42,644,388 as of September 14, 2026.

Key Figures

Planned shares to be sold: 24,999 shares Aggregate market value of planned sale: $2,507,908.44 Class A shares outstanding: 42,644,388 shares +3 more

6 metrics

Planned shares to be sold 24,999 shares Class A shares covered by the Rule 144 notice for Oguzhan Atay

Aggregate market value of planned sale $2,507,908.44 Market value of the 24,999 Class A shares to be sold

Class A shares outstanding 42,644,388 shares Outstanding BillionToOne Class A shares as of September 14, 2026

Sale on July 6, 2026 by Oguzhan Atay 26,250 shares; $3,203,733.13 Class A shares sold and aggregate proceeds on July 6, 2026

Sale on August 3, 2026 by Oguzhan Atay 32,500 shares; $4,450,834.75 Class A shares sold and aggregate proceeds on August 3, 2026

Sale on August 5, 2026 by Oguzhan Atay 15,539 shares; $2,331,351.91 Class A shares sold and aggregate proceeds on August 5, 2026

Key Terms

Rule 144, stock option exercise, Dynasty Trust, 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.

stock option exercise financial

"Class A | 09/14/2026 | 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.

Dynasty Trust financial

"Additionally, there are sales within the past 3 months which occurred in the Atay 2021 Dynasty Trust"

attorney-in-fact regulatory

"as attorney-in-fact for Oguzhan Atay"

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 upcoming share sales?

The Form 144 filing discloses a planned sale of up to 24,999 Class A shares of BillionToOne, Inc. common stock for the account of Oguzhan Atay, in connection with a stock option exercise dated September 14, 2026, to be executed through Fidelity Brokerage Services LLC.

How many BLLN shares are outstanding according to this Form 144?

The notice reports that 42,644,388 Class A shares of BillionToOne, Inc. are outstanding as of September 14, 2026; this figure provides a baseline for understanding the relative size of the potential Rule 144 sale, but it is not the amount being offered.

What recent BLLN share sales by Oguzhan Atay are reported in the last 3 months?

The filing lists several recent sales of BillionToOne Class A shares by Oguzhan Atay, including 26,250 shares on July 6, 2026 for $3,203,733.13, 32,500 shares on August 3, 2026 for $4,450,834.75, and 15,539 shares on August 5, 2026 for $2,331,351.91.

Were there recent BLLN share sales by parties related to Oguzhan Atay?

Yes. The notice states that sales in the past three months occurred in the account of Ezgi N. Akcinar Atay, spouse of Oguzhan Atay, and in the Atay 2021 Dynasty Trust. These related accounts sold Class A shares on July 6 and August 3, 2026, with amounts and proceeds listed in the filing.

What is the nature of the transaction for the new BLLN shares to be sold?

The shares covered by the notice are tied to a stock option exercise with the issuer, dated September 14, 2026, with the form indicating that the consideration for the exercise is cash; the resulting Class A shares may then be sold under Rule 144.

Who signed the BLLN Form 144 and in what capacity?

The Form 144 is signed by /s/ Wade Moss as a duly authorized representative of Fidelity Brokerage Services LLC, acting as attorney-in-fact for Oguzhan Atay, indicating the brokerage is authorized to act on his behalf for these Rule 144 sales.

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

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Available on EDGAR 09/14/2026 - 04:43 PM Accepted by SEC EDGAR 09/14/2026 - 04:35 PM Learn about SEC filing dates

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	0002088549
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	Atay Oguzhan
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
Relationship to Issuer	Director

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	24999	2507908.44	42644388	09/14/2026	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	09/14/2026	Stock Option Exercise	Issuer			24999	09/14/2026	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
Oguzhan Atay 1035 O'Brien Drive Menlo Park CA 94025	Class A	07/06/2026	26250	3203733.13
Ezgi N. Akcinar Atay 1035 O'Brien Drive Menlo Park CA 94025	Class A	07/06/2026	12500	1525645.67
Atay 2021 Dynasty Trust 1035 O'Brien Drive Menlo Park CA 94025	Class A	07/06/2026	2500	300000.00
Oguzhan Atay 1035 O'Brien Drive Menlo Park CA 94025	Class A	07/09/2026	12500	1576276.25
Oguzhan Atay 1035 O'Brien Drive Menlo Park CA 94025	Class A	08/03/2026	32500	4450834.75
Ezgi N. Akcinar Atay 1035 O'Brien Drive Menlo Park CA 94025	Class A	08/03/2026	12500	1717125.00
Atay 2021 Dynasty Trust 1035 O'Brien Drive Menlo Park CA 94025	Class A	08/03/2026	2500	343425.00
Oguzhan Atay 1035 O'Brien Drive Menlo Park CA 94025	Class A	08/05/2026	15539	2331351.91

144: Remarks and Signature

Remarks	There are sales within the past 3 months occurred in the account of Ezgi N. Akcinar Atay, who is the spouse of Oguzhan Atay. Additionally, there are sales within the past 3 months which occurred in the Atay 2021 Dynasty Trust which were made by Icontrust Llc, trustee on the account. Oguzhan Atay is an account stakeholder in the Atay 2021 Dynasty Trust.
Date of Notice	09/14/2026
Date of Plan Adoption or Giving of Instruction, If Relying on Rule 10b5-1	06/05/2026
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/Wade Moss, as a duly authorized representative of Fidelity Brokerage Services LLC, as attorney-in-fact for Oguzhan Atay
ATTENTION: Intentional misstatements or omission of facts constitute Federal Criminal Violations (See 18 U.S.C. 1001)