Company: BLLN
Filing Date: 2025-10-07
Form Type: S-1
Source: 0001193125-25-233697
Chunk: 289

Company: BillionToOne, Inc.
Filing Date: 2025-10-07
Form: S-1
Chunk 289
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 related party has a direct or indirect material interest without the consent of our audit committee. Our audit
committee will have the primary responsibility for reviewing and approving or disapproving such “related party transactions.” The charter of our audit committee will provide that our audit committee shall review and approve in advance
any related party transaction. In approving or rejecting any such transaction, our audit committee is to consider the relevant facts and circumstances available and deemed relevant to our audit committee, including whether the transaction is on
terms no less favorable than terms generally available to an unaffiliated third party under the same or similar circumstances and the extent of the related party’s interest in the transaction.

All of the transactions described in this section were entered into prior to the adoption of this policy. Although we have not had a written policy for the review and
approval of transactions with related parties, our Board of Directors has historically reviewed and approved any transaction where a director or officer had a financial interest, including the transactions described above. Prior to approving such a
transaction, the material facts as to the relationship or interest of the relevant director, officer or holder of five percent or more of any class of our voting securities in the agreement or transaction was disclosed to our Board of Directors. Our
Board of Directors took this information into account when evaluating the transaction and in determining whether such transaction was fair to us and in the best interest of all our stockholders.

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Principal stockholders The following table sets forth the beneficial ownership of our capital stock as of September 30, 2025, and as adjusted to reflect the sale of Class A common stock offered by us in this offering, for:

| • |     | each person, or group of affiliated persons, who is known by us to beneficially own more than 5% of our common stock; |

| • |     | each of our named executive officers; |

| • |     | each of our directors; and |

| • |     | all of our current executive officers and directors as a group. |

We have determined beneficial ownership in accordance with the rules of the SEC. These rules generally attribute beneficial ownership of securities to persons who possess sole or shared voting or investment power with respect to those securities. The information contained in the following table is not necessarily indicative of beneficial ownership for any other purpose, and the inclusion of any shares in the table does not constitute an admission of beneficial ownership of those shares. Unless otherwise indicated by the footnotes below, we believe, based on the information furnished to us, that the persons or