Company: BLLN
Filing Date: 2025-10-17
Form Type: S-1/A
Source: 0001193125-25-242632
Chunk: 286

Company: BillionToOne, Inc.
Filing Date: 2025-10-17
Form: S-1/A
Chunk 286
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 and the Preferred Stock Conversion and the Reclassification, and including, but not limited to, shares subject to outstanding awards under the 2018 Plan, and the issuance of the Class A common stock contemplated to be sold in this offering, but assuming no exercise by the underwriters of their option to purchase additional shares). The number of shares reserved for issuance under our ESPP will automatically be increased on the first day of each of our fiscal years, commencing in 2027 and ending in (and including) 2035, by a number equal to the lesser of:

| • |     | 1% of the shares of Class A common stock outstanding on the last day of the prior fiscal year; or |

| • |     | the number of shares determined by our Board of Directors. |

Notwithstanding the foregoing, no more than 8,400,000 shares of Class A common stock in total may be issued under our ESPP. The number of shares reserved under our ESPP will automatically be adjusted in the event of a stock split, stock dividend or a reverse stock split (including an adjustment to the per-purchaseperiod share limit). Administration The compensation committee of our Board of Directors will administer our ESPP. Eligibility All of our employees will be eligible to participate if we employ them for more than 20 hours per week and for five or more months per year. Eligible employees may begin participating in our ESPP at the start of any offering period. Offering periods Each offering period will last a number of months determined by the compensation committee, not to exceed 27 months. The initial offering period will commence on a date determined by the compensation committee and such date will be determined by the compensation committee at some point following the effectiveness of the registration statement of which this prospectus forms a part. The compensation committee will also determine when additional subsequent offering periods will commence. Offering periods may overlap or may be consecutive. Amount of contributions Our ESPP will permit each eligible employee to purchase Class A common stock through payroll deductions. Each employee’s payroll deductions may not exceed 15% of the employee’s cash compensation. Each participant may purchase up to the number of shares determined by our Board of Directors on any purchase date, not to exceed 7,500 shares. The value of the shares purchased in any calendar year may not exceed $25,000. Participants may withdraw their contributions at any time before stock is purchased. Purchase price The price of each share of Class A common stock purchased under our ESPP will not be less than 85