Companies in the United States can grant two types of stock options: nonqualified stock options (NQSOs), the more common type, and incentive stock options (ISOs), which offer some tax benefits but also raise the complexities of the alternative minimum tax (AMT). The table below summarizes and compares the major traits of NQSOs and ISOs.

Option type Eligibility Event that triggers taxes Taxes Withholding? Tax at sale
NQSOs Company employees, executives, directors, contractors, and consultants Exercise Ordinary income tax, Social Security, and Medicare on the exercise spread Yes, at exercise Capital gains tax
ISOs Only company employees and executives Sale, unless AMT incurred Ordinary income tax, AMT, or and/or capital gains* No Capital gains tax*

*ISO taxation depends on when shares are sold and on the sale price relative to the exercise/purchase price and the market price at exercise. For details, see a related FAQ.