If I understand the rules correctly, an ISO that is exercised more than 90 days after leaving a job is treated as an NSO, which means that it will be taxed at regular income tax rates instead of having the ability to be taxed at long-term cap gains rate. (This could reduce their value by an additional 15%+.)<p>That said, it&#x27;s irrelevant if you exercise and sell an ISO at the same time, because short-term cap gains are taxed as income tax, too.<p>The real interesting term is having the ability to early exercise your entire stock grant, <i>before</i> it vests and before there is a spread between its strike price and fair market value. (The company would have a repurchase right, to implement the vesting schedule.) That way the cost is very low, and there&#x27;s no worry of having to exercise in the future when it could be taxed unfavorably, and the clock for long-term capital gains starts early.