ISO (incentive stock option) 一两年后再卖,可以当作long term capital gain.
"If you exercise your options one year before selling and your grant date was at least two years prior to the date you sell, you’ll only have to pay long term capital gains tax on your profit, rather than the much higher typical income tax rate."
https://www.ycombinator.com/library/Ep-all-about-startup-equity?