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.