Company: BLLN
Filing Date: 2025-10-07
Form Type: S-1
Source: 0001193125-25-233697
Chunk: 281

Company: BillionToOne, Inc.
Filing Date: 2025-10-07
Form: S-1
Chunk 281
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 outstanding on the last business 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. A new offering period will begin periodically, as determined by the compensation committee. 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% of the lower of the fair market value per share of Class A common stock on the first day of the applicable offering period or the fair market value per share of Class A common stock on the purchase date. 212

Other provisions

Employees
may end their participation in our ESPP at any time. Participation ends automatically upon termination of employment with us. If we experience a change in control, our ESPP will end and shares will be purchased with the payroll deductions
accumulated to date by participating employees. Our Board of Directors or our compensation committee may amend or terminate our ESPP at any time.

213

Certain relationships and related party transactions The following is a description of transactions since January 1, 2022, or currently proposed, to which we have been or will be a participant, in which the amount involved exceeded $120,000 and in