Financial Glossary
Vesting Acceleration
Vesting acceleration is a contractual provision that causes unvested equity -- stock options, restricted stock units, or founder shares -- to vest earlier than the scheduled cliff or graded timeline, typically triggered by a defined event. Single-trigger acceleration vests shares upon a single event, most commonly a company acquisition or change of control. Double-trigger acceleration requires two events to occur: a change of control followed by an involuntary termination of the employee. Acceleration provisions are negotiated at grant, reflected in equity award agreements or employment contracts, and affect both the economic outcome for the recipient and the acquirer's cost model when pricing a deal.
Problem & Application
An early engineer joins a startup and receives 100,000 stock options vesting over four years with a one-year cliff. After 18 months, the company is acquired. Without an acceleration clause, 37,500 options (18/48 of the total) are vested and the remaining 62,500 are unvested -- potentially forfeited or converted to acquirer equity on the acquirer's timeline. With a double-trigger provision, the 62,500 unvested options accelerate fully only if the acquirer also terminates or materially demotes the engineer within a defined window (often 12 months) post-close. This protects the employee from being retained just long enough to forfeit unvested equity before being let go. From the acquirer's perspective, full single-trigger acceleration across all employees increases the acquisition consideration because it accelerates compensation cost, so acquirers often negotiate to remove or limit it, particularly when retention of the team is a core rationale for the deal.
In Short
Vesting acceleration can be a powerful tool for employee retention, particularly during acquisitions. Proper planning ensures that it is applied fairly and within the parameters of the company’s compensation strategy.