Post-Termination Exercise Window

The period after leaving a company during which you can still exercise vested stock options — most commonly 90 days, though some companies offer years.

The post-termination exercise window (PTEW) is the period after your employment ends during which you can exercise your vested stock options. Once this window closes, unexercised options expire worthless — regardless of their underlying value. The standard window is 90 days, which is the minimum permitted under tax rules for ISOs to maintain their favorable tax treatment. Many employees who leave before an IPO discover that the 90-day window creates an impossible financial dilemma: exercise options that may be illiquid for years, or lose them.

The problem is most acute at pre-IPO startups where options have a high strike price and a high 409A valuation. To exercise, you must pay the strike price (times the number of options) plus taxes on the spread between the strike and the 409A value — all in cash, immediately. A software engineer with 100,000 vested ISOs at a $5 strike and a $25 409A faces a $500,000 exercise cost plus AMT exposure of up to $2M in phantom income. For most employees, this is simply not possible.

A growing number of companies — particularly those backed by employee-friendly investors — have extended their PTEW to 5 or 10 years after departure. Coinbase, Stripe, Pinterest, and others have made longer windows available. A longer PTEW decouples the liquidity decision from the exercise decision: you can wait until you know whether the company will succeed before committing capital. When evaluating startup equity, asking about the PTEW is as important as asking about the vesting schedule.

The 90-Day Problem

  • 90-day window = you must decide to exercise within 3 months of your last day.
  • Exercising costs money upfront: number of options × strike price, plus taxes on the spread.
  • If the company is still private, you're paying real money for illiquid shares that may take years to be worth anything.
  • The 90-day limit exists because ISO tax treatment requires exercise within 90 days of termination — options held longer are automatically reclassified as NSOs, losing favorable tax treatment.
  • NSOs don't have the same 90-day tax rule — but most plans use the same window for simplicity.

Questions to Ask Before Joining

  • What is the post-termination exercise window?
  • Is the window the same for all employees, or extended for certain grant types or tenures?
  • If I exercise early (while still employed), is the window irrelevant?
  • What is the current 409A valuation, and how does that compare to the preferred share price?
  • Is the company planning to extend the PTEW for all employees?

Example

A senior engineer spent 3.5 years at a unicorn startup. She holds 200,000 vested ISOs at a $3 strike price; the 409A value is $40/share. She resigns and has 90 days to decide. Exercise would cost $600,000 (strike) plus face AMT on $7.4M of spread — she simply cannot afford it. Her 200,000 vested options, which represent real potential value if the company IPOs, expire worthless because of the 90-day window. A company with a 5-year PTEW would have given her time to wait for liquidity.