the irs defines the rules for an ISO, so to be incentivized it must exercised within 90 days of leaving. with an NSO(or ISO), the limit is ten years from grant

the irs defines the rules for an ISO, so to be incentivized it must exercised within 90 days of leaving. with an NSO(or ISO), the limit is ten years from grant, again set by the irs - you can still be employed and have to deal with this. until recently, companies typically gave ISO - this means they had to do ninety days. so first, blame goes towards the IRS. ISO are generally more favorable because you dont owe regular income tax at exercise - with NSO you do owe tax on the difference between grant and FMV prices, even if you can't sell it. However, AMT does not recognize ISOs so you may owe AMT against that same difference. AMT is weird though, you can get that money back over future years by claiming tax credits luckily, the trend seems to be to convert ISO to NSO and extend the expiration, but thats still a relatively new change and not everywhere.