The post-termination exercise period (PTEP) is the limited time — historically 90 days, increasingly extended to several years — in which a departing employee can exercise vested options before forfeiting them. A short window can force employees to pay the strike price and tax immediately or lose the options.
Founders increasingly offer extended PTEPs to make equity genuinely valuable to early employees, though extending past 90 days converts incentive stock options (ISOs) into non-qualified options for U.S. tax purposes — a trade-off to weigh when designing an option plan.
The exercise window trap
The post-termination exercise period is the window — classically 90 days — within which a departing employee must exercise vested options or lose them. It is one of the harshest mechanics in startup equity, because exercising often means paying both the strike price and a tax bill on illiquid shares the employee cannot yet sell. Many people forfeit options they genuinely earned simply because they cannot fund the exercise in time. In response, some companies adopt an extended PTEP (for example several years), trading a cleaner cap table for fairer treatment of leavers. On US grants the choice also affects tax status, since incentive stock options convert to non-qualified options if exercised beyond set periods.
PTEP as a real economics term
The post-termination exercise period quietly decides what options are worth. The classic 90-day window forces a departing employee to pay the strike price and the tax bill on illiquid shares within three months or forfeit everything — economically, a retention device dressed as a deadline. The extended-window movement (5–10 years, pioneered by several US scale-ups) trades that pressure for goodwill, with the US tax wrinkle that ISOs convert to NSOs after 90 days. In Turkish-style phantom plans the analogue is the payment trigger and forfeiture design for leavers — good-leaver/bad-leaver definitions doing the work the PTEP does in option plans. Whatever the instrument: the leaver table is the clause employees actually live, and diligence reads inconsistencies between offer letters, plan rules and practice as findings.
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