Single- and double-trigger acceleration
What happens to unvested stock when the company is sold: no acceleration, single trigger or double trigger, worked on one founder's block.
Acceleration vests unvested stock early when something happens — almost always a sale of the company. Take a sale in month 30: each Northwind founder has 2,500,000 shares vested and 1,500,000 still unvested. What happens to the unvested shares is the whole clause.
No acceleration
- Good at
- Keeps the incentive to stay through an integration
- Nothing for a buyer to price around
- Watch for
- A buyer acquiring the team may find the founders leave the day after closing
- Nothing protects the holder if the buyer lets them go
- Best for
- Rarely anyone's first choice
Single trigger
- Good at
- Certain: the sale alone vests the stock
- No dispute about whether a termination was 'for cause'
- Watch for
- The team is fully vested the day a buyer needs them most
- Buyers often ask for new vesting, which undoes it
- Best for
- Narrow cases, such as a director or advisor whose role ends with the sale
Double trigger
- Good at
- Protects the holder if the buyer lets them go
- The buyer keeps the incentive for those it keeps
- Watch for
- Turns on definitions — cause, good reason, the window after closing
- Partial acceleration (a fraction) protects less
- Best for
- Founders and key hires — the clause investors most often accept
Where this lesson's rules come from
The sources behind this lesson's requirements, by kind. Background reading explains; it is never the authority for a rule. Anything marked as a convention is ours, not the rule-maker's.
- Background reading — not an authority
- Wikipedia, “Vesting” (opens in a new tab)Vesting, cliffs and single- and double-trigger acceleration — backgroundFree to read
- NVCA Model Certificate of Incorporation (Oct. 2025), §3.3 (Preferred Stock Protective Provisions) (opens in a new tab)Protective provisions: what the company may not do without the preferredFree to read
The words this page teaches
Each links to its glossary definition, which also names the authority behind it and the components that render it.
- AccelerationA clause that vests unvested equity early. Single-trigger accelerates on one event, usually a sale of the company; double-trigger needs a second, usually the holder's termination without cause within a set period after the saleConvention
- VestingEarning equity over time, so a holder who leaves keeps only what has vested. The common schedule is four years with a one-year cliff: nothing for twelve months, a quarter on the first anniversary, then monthly to month 48Convention