BillionToOne director plans sale of 5,332 shares

Form 144 reports a proposed sale of 5,332 BillionToOne Class A shares linked to officer Oguzhan Atay, alongside recent family and trust share sales.

Rhea-AI Filing Summary

BillionToOne, Inc. (BLLN) has a Form 144 notice indicating that securities beneficially associated with officer and director Oguzhan Atay are being proposed for sale under Rule 144. The notice covers the potential sale of 5,332 Class A shares of pre-IPO stock through Fidelity Brokerage Services LLC and lists prior sales in the last three months by his spouse and the Atay 2021 Dynasty Trust.

Key Figures

Shares to be sold under Rule 144: 5,332 shares Aggregate market value of shares to be sold: $522,536.00 Shares outstanding: 42,644,388 shares +3 more

6 metrics

Shares to be sold under Rule 144 5,332 shares Class A shares covered by this Form 144 notice

Aggregate market value of shares to be sold $522,536.00 Value of the 5,332 Class A shares referenced in the notice

Shares outstanding 42,644,388 shares Approximate Class A shares outstanding as of September 14, 2026

Sale on July 6, 2026 by Oguzhan Atay 26,250 shares for $3,203,733.13 Class A shares sold in the past three months

Sale on August 3, 2026 by Oguzhan Atay 32,500 shares for $4,450,834.75 Class A shares sold in the past three months

Sale on August 5, 2026 by Oguzhan Atay 15,539 shares for $2,331,351.91 Additional Class A sale disclosed for the past three months

Key Terms

Rule 144, Form 144, pre-IPO shares, trustee, +1 more

5 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.

Form 144 regulatory

"144: Filer Information"

Form 144 is a document that investors must file with the government when they plan to sell a large number of shares of a company's stock. It helps ensure transparency so everyone knows how many shares are being sold and when, which can impact the stock's price.

pre-IPO shares financial

"Class A | 05/01/2024 | Pre-IPO shares | Issuer"

trustee financial

"which occurred in the Atay 2021 Dynasty Trust which were made by Icontrust Llc, trustee"

A trustee is a person or institution legally appointed to hold and manage assets or enforce an agreement on behalf of other people (beneficiaries). Think of a trustee as a neutral referee or custodian who must act in the beneficiaries’ best interests, follow the trust or contract rules, and handle distributions, recordkeeping and enforcement. Investors care because a trustworthy trustee protects their rights, ensures promised payments or remedies are delivered, and can influence recoveries if things go wrong.

attorney-in-fact regulatory

"as a duly authorized representative of Fidelity Brokerage Services LLC, as attorney-in-fact"

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 BillionToOne (BLLN) disclose in this Form 144 filing?

The filing reports a proposed sale under Rule 144 of 5,332 Class A shares of BillionToOne, Inc. pre-IPO stock, to be sold through Fidelity Brokerage Services LLC, by or for the account of parties associated with officer and director Oguzhan Atay.

How many BillionToOne (BLLN) shares are covered by this specific Form 144 notice?

This notice covers a proposed sale of 5,332 Class A shares of BillionToOne, Inc. These shares are described as pre-IPO shares and are to be sold for cash under Rule 144 with Fidelity Brokerage Services LLC as broker.

What recent BillionToOne (BLLN) share sales related to Oguzhan Atay are disclosed?

The document lists several past 3‑month sales, including 26,250 Class A shares sold on July 6, 2026 for $3,203,733.13 and 32,500 Class A shares sold on August 3, 2026 for $4,450,834.75 in accounts associated with Oguzhan Atay.

Who else besides Oguzhan Atay is involved in recent BillionToOne (BLLN) sales?

The filing notes sales in the past three months by Ezgi N. Akcinar Atay, the spouse of officer and director Oguzhan Atay, and by the Atay 2021 Dynasty Trust, for which Icontrust LLC is trustee and Atay is an account stakeholder.

What does the Form 144 say about BillionToOne (BLLN) shares outstanding?

The notice states that there were approximately 42,644,388 Class A shares outstanding as of September 14, 2026; this is provided as context for the Rule 144 sale and is not the number of shares being sold.

What type of BillionToOne (BLLN) shares are being sold and how will they be sold?

The securities to be sold are Class A pre-IPO shares of BillionToOne, Inc., with the proposed sale date of May 1, 2024, for cash. The sales are to be executed through Fidelity Brokerage Services LLC under Rule 144.

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

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Available on EDGAR 09/14/2026 - 11:57 AM Accepted by SEC EDGAR 09/14/2026 - 11:56 AM 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	Member of immediate family of any of the foregoing

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	5332	522536.00	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	05/01/2024	Pre-IPO shares	Issuer			5332	05/01/2024	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	Today's sale and sales within the past 3 months occurred in the account of Ezgi N. Akcinar Atay, who is the spouse of Oguzhan Atay, an Officer and Director of the company. There are also 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	06/07/2026
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)