Company: BLLN
Filing Date: 2025-09-17
Form Type: DRS/A
Source: 0001193125-25-206347
Chunk: 302

Company: BillionToOne, Inc.
Filing Date: 2025-09-17
Form: DRS/A
Chunk 302
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 the public information requirements of Rule 144. To be an eligible stockholder under Rule 144, such stockholder must not be deemed to have been one of our affiliates for purposes of the Securities Act at any time during the 90 days preceding a sale and must have beneficially 224

owned the shares proposed to be sold for at least six months, including the holding period of any prior owner other than our affiliates. If such a person has beneficially owned the shares proposed to be sold for at least one year, including the holding period of any prior owner other than our affiliates, then such person is entitled to sell such shares without complying with any of the requirements of Rule 144, subject to the expiration of the lock-upagreements and/or market stand-offarrangements described below, which prevent the sale of shares. In general, under Rule 144, as currently in effect, our affiliates or persons selling shares on behalf of our affiliates are entitled to sell shares on expiration of the lock-upagreements and/or market standoff arrangements described below, subject, in the case of restricted securities, to such shares having been beneficially owned for at least six months. Beginning 90 days after the date of this prospectus, within any three-month period, such stockholders may sell a number of shares that does not exceed the greater of:

| • |     | 1% of the number of shares of common stock then outstanding, which will equal    shares immediately                             
 after this offering, assuming no exercise of the underwriters’ option to purchase additional shares of common stock from us; or |

| • |     | the average weekly trading volume of our common stock during the four calendar weeks preceding the filing of a notice on 
 Form 144 with respect to such sale.                                                                                      |

Sales under Rule 144 by our affiliates or persons selling shares on behalf of our affiliates are also subject to certain manner of sale provisions and notice requirements and to the availability of current public information about us. Rule 701 Rule 701 under the Securities Act, or Rule 701, generally allows a stockholder who was issued shares under a written compensatory plan or contract and who is not deemed to have been an affiliate of our company during the immediately preceding 90 days, to sell these shares in reliance on Rule 144, but without being required to comply with the public information, holding period, manner of sale limitations, volume limitation, or notice provisions of Rule 144. Rule 701 also permits affiliates of our company to