TLDR:
Double trigger acceleration is a vesting provision where unvested equity accelerates only if two conditions are met: a company acquisition AND the employee’s termination or significant role change without cause.
vs. Single Trigger
Single trigger: equity accelerates on acquisition alone.
Double trigger: requires both acquisition AND adverse employment event.
Single vs. Double Trigger — The Negotiation
The choice between single and double trigger acceleration is one of the most contentious negotiation points in M&A transactions involving startups with employee equity. Acquirers typically prefer double trigger because they want to retain key employees post-acquisition using unvested equity as a retention tool. Founders and employees naturally prefer single trigger because it provides full value in an acquisition regardless of what happens to their employment.
Single Trigger vs. Double Trigger
Single-trigger acceleration vests options or restricted stock immediately upon a change of control, regardless of subsequent employment. Double-trigger requires both a change of control AND a subsequent involuntary termination (or material adverse change in role) within a specified period. Double trigger is heavily preferred by acquirers because it preserves retention incentives — key employees must stay to fully vest. Founders typically negotiate at least partial single-trigger for their own grants while accepting double-trigger for other employees.
Acceleration Negotiation Points
Acceleration provisions vary in scope: full acceleration (100% of unvested equity), partial acceleration (typically 50%–100%), or time-weighted acceleration (additional vesting tied to time elapsed). Founders should negotiate the precise definitions of “change of control” (covering both sales and major reorganizations), “good reason” termination (covering role demotion, geographic relocation, and compensation reduction), and the time period during which double-trigger termination triggers acceleration (typically 12–24 months post-closing).