# 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.

Source: https://lopifi.com/learn/founder-stock-and-vesting/single-and-double-trigger-acceleration
Part of: Lopifi — US GAAP books on autopilot, checked by a CPA (https://lopifi.com)

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**What is single-trigger vs 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](https://lopifi.com/md/glossary/acceleration) vests [unvested](https://lopifi.com/md/glossary/vesting) 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.

| Clause | What happens | Vested | Still unvested |
| --- | --- | --- | --- |
| None | Vesting simply continues under the buyer — if the buyer keeps the agreement | 2,500,000 | 1,500,000 |
| Single trigger | The sale alone vests everything | 4,000,000 | 0 |
| Double trigger, kept on | The sale is one trigger; no second | 2,500,000 | 1,500,000 |
| Double trigger, let go | Sale, then termination without cause | 4,000,000 | 0 |

One founder's 4,000,000 shares at a sale in month 30, full acceleration where it fires.

*[Figure: vesting]*

Month 30 of 48 on a founder's schedule: the solid steps are vested, the wireframe ones are what an acceleration clause is about.

**No acceleration**
- Pro: Keeps the incentive to stay through an integration
- Pro: Nothing for a buyer to price around
- Con: A buyer acquiring the team may find the founders leave the day after closing
- Con: Nothing protects the holder if the buyer lets them go
- Best for: Rarely anyone's first choice

**Single trigger**
- Pro: Certain: the sale alone vests the stock
- Pro: No dispute about whether a termination was 'for cause'
- Con: The team is fully vested the day a buyer needs them most
- Con: 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**
- Pro: Protects the holder if the buyer lets them go
- Pro: The buyer keeps the incentive for those it keeps
- Con: Turns on definitions — cause, good reason, the window after closing
- Con: Partial acceleration (a fraction) protects less
- Best for: Founders and key hires — the clause investors most often accept

Which clause, from where each side sits

> **Investors read this clause.** The NVCA model charter lists, among the optional protective provisions, approving an equity grant to a 1% holder that provides for acceleration or vests on anything other than four years with a one-year cliff. Acceleration is negotiated, not assumed.

> “increase [or decrease] the authorized number of shares of Common Stock, Preferred Stock, or any series thereof;”

— [NVCA Model Certificate of Incorporation (Oct. 2025), §3.3 (Preferred Stock Protective Provisions)](https://nvca.org/model-legal-documents/), Protective provisions: what the company may not do without the preferred

— [Wikipedia, “Vesting”](https://en.wikipedia.org/wiki/Vesting), Vesting, cliffs and single- and double-trigger acceleration — background

## Where this page's rules come from

- [Wikipedia, “Vesting”](https://en.wikipedia.org/wiki/Vesting) — Vesting, cliffs and single- and double-trigger acceleration — background (reference)
- [NVCA Model Certificate of Incorporation (Oct. 2025), §3.3 (Preferred Stock Protective Provisions)](https://nvca.org/model-legal-documents/) — Protective provisions: what the company may not do without the preferred (reference)

- **Track:** [Cap tables & raising](https://lopifi.com/md/learn/equity)
- **Part of:** [Founder stock, vesting and the 83(b) election](https://lopifi.com/md/learn/founder-stock-and-vesting) — 5 min
- **Terms taught:** [Acceleration](https://lopifi.com/md/glossary/acceleration), [Vesting](https://lopifi.com/md/glossary/vesting)
- **Previous:** [The 83(b) election, step by step](https://lopifi.com/md/learn/founder-stock-and-vesting/83b-election)
- **Next:** [The cap table explained, Cap table · Lesson 2](https://lopifi.com/md/learn/cap-table-explained)
- **The course:** https://lopifi.com/md/learn