Company: BLLN
Filing Date: 2025-09-17
Form Type: DRS/A
Source: 0001193125-25-206347
Chunk: 301

Company: BillionToOne, Inc.
Filing Date: 2025-09-17
Form: DRS/A
Chunk 301
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 of Class A common stock that we are selling in this offering, which shares may be resold in the public market immediately unless purchased by our affiliates, and assumes no additional exercise of outstanding options or warrants other than as described elsewhere in this prospectus. The remaining shares of our Class A common stock and all of the shares of our Class B common stock will be “restricted securities,” as that term is defined in Rule 144. Restricted securities are eligible for public sale only if they are registered under the Securities Act or if they qualify for an exemption from registration under Rules 144 or 701 under the Securities Act, which are summarized below. Substantially all of these shares will be subject to a lock-upperiod under the lock-upagreements and market stand-offagreements described below. As a result of these lock-upand market stand-offagreements, and subject to the provisions of Rules 144 or 701, shares of our Class A common stock will be available for sale in the public market as follows (assuming no exercise of outstanding stock options subsequent to June 30, 2025):

| • |     | beginning on the date of this prospectus, all shares of our Class A common stock sold in this offering will be 
 eligible for immediate sale in the public market, unless purchased by our affiliates; and                      |

| • |     | beginning 180 days after the date of this prospectus,    additional shares of Class A common                                                                                                  
 stock and      shares of Class A common stock issuable upon the conversion of outstanding Class B common stock will become eligible for sale in the public market, of which    shares will be 
 held by affiliates and subject to the volume, manner of sale, and other restrictions of Rule 144, as described below.                                                                         |

In addition, after this offering, up to shares of Class A common stock may be issued upon exercise of outstanding stock options as of June 30, 2025, and shares of Class A common stock are available for future issuance under our 2018 Plan. Rule 144 In general, under Rule 144 as currently in effect, once we have been subject to public company reporting requirements of Section 13 or Section 15(d) of the Exchange Act for at least 90 days, an eligible stockholder is entitled to sell such shares without complying with the manner of sale, volume limitation, or notice provisions of Rule 144, subject to compliance with