網絡學習後的總結，理解不當請原諒，僅供參考。
For example, $10 stock option grant price for 2000 shares, vesting in 4 years.
Grant date: generally no tax implications.
Exercise date: normally upon termination of employment. Say after 3 year of grant date. Buy $10 x 1500 vested shares. Company will issue Form 3921 to show grant price $10, fair value on exercise date (say $30), and 1500 shares exercised.
No ordinary income tax but employee will need to calculate the AMT (alternative minimum tax) based on the difference between fair value $30 and cost $10 times 1500 shares x AMT tax rate. The cost basis of these stock option AMT will be $30 per share in the future.
Selling date: say selling these 1500 shares after IPO at $210. Capital gain = ($210 - $10)x1500 = $300,000; AMT based on ($210 - $30 ) x 1500 x AMT tax rate. Broker will issue Form 1099-B.
由於AMT, Exercise stock option 也有稅務風險。在2000年網絡股票泡沫期間，有員工獲$1 x 50,000公司股權，在上市前估值到一股$100（409A fair value)時Execise換為股票，繳了幾十萬的AMT，不料上巿後不久公司股價大跌成仙股。白白打工幾年繳了AMT。狼會吃肉，也會挨揍！
