Single-Trigger Acceleration

A vesting provision that accelerates some or all unvested equity automatically on a company acquisition or change of control — regardless of what happens to the employee's job afterward.

Single-trigger acceleration is a vesting provision that causes unvested equity to vest immediately upon a single event: a change of control such as an acquisition, merger, or asset sale. Unlike double-trigger acceleration — which requires both an acquisition AND subsequent job loss — single-trigger acceleration fires on the acquisition alone. From the employee's perspective, this is maximally protective: no matter what the acquirer does with their employment, the unvested equity is already fully vested as of the acquisition close. From the acquirer's perspective, single-trigger acceleration is highly problematic: it eliminates the entire equity-based retention incentive that makes acquisition talent retention possible, and the cost is often factored into the deal price as a liability.

Because of acquirer resistance, single-trigger acceleration in its pure form — 100% of all unvested equity accelerates on acquisition alone — is rare below the C-suite. It does appear in several contexts: for founders who may have meaningful unvested equity even late in the company's life, for early employees who negotiated unusually strong terms, for C-suite executives whose departures are considered likely post-acquisition (making retention leverage less valuable to an acquirer), and in older grant agreements from an era when the provision was more common. In some cases, a company board will approve single-trigger acceleration for a particular executive as part of a package designed to retain them through an acquisition process — where the executive's full cooperation in the sale is more valuable than their post-acquisition retention.

A common variation is 'partial single-trigger' acceleration — for example, 12 or 24 months of unvested equity accelerates on acquisition, rather than 100%. This compromise gives employees meaningful protection and the company's board the ability to negotiate with prospective acquirers by showing that some retention incentive remains in the unvested portion. Another variation is 'single-trigger acceleration, acquirer option to substitute': the acceleration applies unless the acquirer offers a substantially equivalent equity package in replacement — most acquirers elect to substitute, which effectively turns the single trigger into a double trigger for the replacement grants.

The practical significance of single-trigger vs. double-trigger depends heavily on the acquisition scenario. In a friendly acquisition where the acquirer wants to retain most employees, double-trigger protection is usually sufficient — you'll keep your job, and the unvested equity will continue vesting. Single-trigger matters most when the acquirer's primary interest is the company's IP, customer base, or technology, and most employees are expected to be integrated or let go quickly. In 'acqui-hire' scenarios — where the acquirer is purchasing primarily the engineering team — single-trigger provisions, if they exist, may be bypassed by acquirers who negotiate directly with key individuals or restructure the transaction to avoid triggering the provision. Reading your grant agreement carefully before a company acquisition is essential.

When Single-Trigger Acceleration Appears

  • Founder grants: founders often negotiate strong acceleration because their equity represents years of pre-funding work and they may not remain with the acquirer.
  • C-suite and executive level: CEOs, CFOs, and other executives whose departure is expected or even desired by acquirers sometimes receive single-trigger or hybrid provisions.
  • Older grant agreements: single-trigger was more common in pre-2010 startup culture; if you have old grants, check your original agreement.
  • Board-approved retention packages: boards sometimes grant single-trigger acceleration to specific executives to incentivize cooperation with an acquisition process.
  • Advisor grants: advisors who provide limited ongoing services may receive single-trigger acceleration since there's no meaningful retention value to maintain.
  • Partial single-trigger compromise: 12-24 months of unvested equity accelerating on acquisition, with the remainder on a double-trigger basis.

Why Acquirers Resist Single-Trigger

  • It destroys the primary employee retention tool: if all equity vests at close, employees have little financial reason to stay post-acquisition.
  • The cost shows up in the deal: acquirers often reduce their offer price by the estimated cost of acceleration — what looks like a windfall for employees reduces the company's sale price.
  • Retention risk is highest in acqui-hires: where the people ARE the asset being acquired, single-trigger provisions that allow key people to cash out and leave immediately undermine the rationale for the deal.
  • Substitute equity packages: acquirers often condition single-trigger waiver on providing a replacement equity grant with equivalent value — allowing them to restructure retention incentives on their own schedule.
  • Board fiduciary duty tension: boards have a duty to maximize shareholder value; granting single-trigger to executives increases acquisition costs, which can reduce the available consideration for common shareholders.

Single-Trigger vs. Double-Trigger: Choosing Your Negotiating Position

  • If you're negotiating a senior offer, push for double-trigger first — it's the market standard and easier to get than single-trigger.
  • Single-trigger is most worth pushing for if you have specific reason to expect you won't remain post-acquisition (your role has a clear successor at any large acquirer, your company is a likely M&A target in a consolidating industry).
  • If an acquirer requires you to waive a single-trigger provision, negotiate for a cash retention bonus equivalent to the unvested equity value — acquirers often pay these to close deals.
  • Hybrid provisions (some single, most double) are the realistic middle ground: ask for single-trigger on 25-50% of unvested equity with double-trigger on the remainder.
  • Document everything: verbal assurances about acceleration do not bind the company or acquirer — only written provisions in the grant agreement or offer letter are enforceable.

Example

A startup's CTO was granted 1,000,000 unvested options with single-trigger acceleration when he joined as employee #3. Four years later, the company is acquired for $200M. At close, he has 250,000 unvested options remaining. His single-trigger provision fires: those 250,000 options vest immediately at close. With a strike price of $0.10/share and an acquisition price of $8/share, he receives $1.975M in additional proceeds on the accelerated options. The acquirer had tried to negotiate away the single-trigger clause and offer replacement RSUs vesting over three years, but his counsel held firm on the agreement language. He chose to remain with the acquirer for a year anyway (he received a retention bonus for doing so), but the fact that his unvested equity was secured regardless gave him meaningful negotiating leverage. Most of his colleagues — who had standard double-trigger provisions — received equivalent treatment only because the acquirer wanted to retain the whole team.