Single-Trigger Acceleration

A single-trigger acceleration clause forces the automatic vesting of an employee’s unvested equity—typically a large portion or 100% of remaining shares—the moment a change of control (such as an acquisition) is announced or closes, regardless of whether the employee remains employed. It is the opposite of conditional vesting, and far more valuable to the recipient.

Why single-trigger is rare but sought-after

Single-trigger acceleration is the equity equivalent of a lottery win for employees. On the day the deal closes—or sometimes just when it is announced—all remaining unvested shares or options become theirs. An employee with four years on the vesting schedule who gets laid off before the deal might have only 25% of their equity vested. Single-trigger turns the remaining 75% into immediate cash or liquid stock. For obvious reasons, employers rarely grant this, and acquirers actively resist it.

Single-trigger clauses tend to appear only in narrowly negotiated situations: founder stock grants, C-level executive packages at acquisition-prone companies, or as a condition of an employee joining a company explicitly known to be in acquisition discussions. Ordinary employees almost never see single-trigger acceleration.

The cost to the acquirer is steep. If a company with 500 employees closes a deal, and each employee has an average of $50,000 in unvested equity, single-trigger could trigger $25 million in immediate payouts just from vesting. Some of those employees will leave shortly after the deal anyway, so the company has just paid for retention it did not need.

The mechanics: what “change of control” means

Change of control is typically defined in the equity documents and varies slightly between companies. Common definitions include:

• Sale of more than 50% (sometimes 30% or 40%) of the company’s voting stock
• Sale or transfer of substantially all (usually 80–90%) of the company’s assets
• Merger in which shareholders lose control (including reverse mergers)
• Appointment of a majority of the board of directors by an outside party

The date of activation is usually the closing of the transaction, though some agreements say the acceleration occurs upon announcement or shareholder approval. Once the trigger fires, all eligible equity vests immediately. There is no waiting period, no employment condition to satisfy.

Full vesting vs. partial

Some single-trigger clauses accelerate 100% of unvested equity. Others provide for a percentage—typically 50% to 75%—leaving some equity subject to the original vesting schedule or to double-trigger acceleration if the employee is later terminated.

A partial-acceleration arrangement might say: “Upon a change of control, 50% of unvested shares vest immediately; the remaining 50% vests only if the employee is involuntarily terminated within 24 months.” This is a hybrid approach, reducing the buyer’s immediate payout while still protecting the employee against a post-deal layoff.

Single-trigger vs. double-trigger: the employee perspective

An employee with single-trigger acceleration wants only one thing to happen: the company to be acquired. Employment continuity is irrelevant. If the deal closes and the buyer immediately restructures the entire department, the employee still gets the full payout.

An employee with double-trigger acceleration must hope for two things: acquisition AND being fired. If the company is acquired and they are kept on, their unvested equity stays frozen on the original schedule. This is why single-trigger is drastically more valuable—it removes the employment contingency.

For founders and executives in competitive fundraising environments, single-trigger can be a negotiating point. “If you want me to agree to this lower salary, give me single-trigger acceleration in the equity.” It shifts risk from job loss to acquisition likelihood alone.

Why acquirers dislike it

From the buyer’s perspective, single-trigger acceleration is a financial liability and a talent problem.

Financially, it triggers a large, immediate payout. If the deal assumes the company has X employees with Y equity outstanding, and 80% of that equity vests on close, the buyer’s integration costs spike. In some cases, the purchase agreement forces the seller to set aside cash for these payouts before the buyer takes control.

Talent-wise, single-trigger can backfire. An employee with fully accelerated equity may feel no obligation to stay and help integrate the company. They got their windfall; why work nights and weekends on the buyer’s systems? Paradoxically, the provision intended to retain people can accelerate departures. The acquirer ends up paying for employees who leave on day one.

Acquirers often insist on double-trigger instead, or on lower acceleration percentages. The negotiation between seller and buyer often hinges on these terms.

Interaction with share price and equity type

The cash value of single-trigger acceleration depends on the form of equity and the deal price. Options become valuable (if out of the money) because the acquirer typically pays them out at spread to the deal price or fair market value. Restricted shares or restricted stock units (RSUs) vest at their grant price and are often converted to the acquirer’s equity or cash.

The purchase agreement usually specifies how unvested equity is treated. Some deals pay out all accelerated equity at fair market value; others convert it to the buyer’s stock at a formula ratio. Employees need to read the purchase agreement closely, because the payout method matters as much as the acceleration percentage.

Drafting considerations

Single-trigger clauses must define:

• Exact definition of change of control (percentage thresholds for stock sale, asset sale, or board control)
• Effective date (announcement, shareholder approval, or closing)
• Percentage of equity that accelerates (100% or a stated percentage)
• Treatment of different equity types (do options, RSUs, and restricted shares all accelerate equally?)
• Whether the clause applies to all employees or only certain tiers (executives, founders, etc.)
• Any cap on total acceleration payout

Vague language (“upon any significant business change”) can trigger disputes about whether a particular event qualifies as a change of control.

See also