Incentive Stock Options
The tax-advantaged grant that rewards patience if you navigate the AMT.
- Who can receive
- Employees only
- Tax at exercise
- AMT adjustment item (spread)
- AMT rates (2026)
- 26% up to $244,500; 28% above
- Tax at sale
- LTCG if holding periods met
- LTCG holding period
- 1 yr from exercise + 2 yrs from grant
- Annual ISO exercisability limit
- $100K FMV first exercisable per calendar year
How it works
An ISO is a contractual right to purchase shares at a price set on the grant date: the strike price. That price must equal the fair market value of the stock at grant, as determined by a 409A valuation. You don't own shares until you exercise. Exercising means paying the strike price for each share. The spread, the difference between the current FMV and your strike price, is what holds value. Until exercise, you hold an option, not equity.
AMT and the phantom tax problem
Under the regular federal tax system, exercising an ISO does not trigger a taxable event. However, the 'bargain element' or spread, the difference between the FMV on the exercise date and the strike price, must be added back to your income for the Alternative Minimum Tax calculation. The AMT applies a 26% rate to AMT-taxable income up to $244,500, with a 28% rate above that threshold (2026 figures). Because this AMT liability is triggered before you sell any shares, a large ISO exercise can create an immense, immediate tax bill on paper gains that remain entirely illiquid, commonly called 'phantom tax.'
Qualifying vs. disqualifying dispositions
If you hold shares for at least one year from exercise and two years from grant date, your sale is a 'qualifying disposition' and gains are taxed at long-term capital gains rates. Selling before either threshold is a 'disqualifying disposition': the spread at exercise is recharacterized and taxed at ordinary income rates in the year of sale, eliminating the tax benefit of the ISO structure. Under IRC 422(d), ISOs that become first exercisable in a single calendar year are subject to a $100K aggregate FMV cap (measured at grant date). Options exceeding this threshold automatically convert to NSOs, a detail often overlooked in large grants.
Common questions
Do I owe taxes when my ISOs vest?
No. Vesting does not trigger a tax event. The tax clock starts at exercise, not at vesting.
What is the ISO AMT trap?
When you exercise ISOs, the spread between your strike price and the current FMV is an AMT adjustment under IRC Section 56(b)(3). If that spread is large, you may owe Alternative Minimum Tax in the exercise year even though you haven't sold any shares, meaning you'd need cash to pay a tax bill on paper gains. This is why exercising ISOs early, when the spread is small, is a common strategy.
What happens to my ISOs if I leave the company?
Most plans give you 90 days after termination to exercise your vested ISOs. After 90 days, they either expire or convert to NSOs depending on plan terms. After conversion to NSOs, you lose the ISO tax treatment. The spread at exercise becomes ordinary income.
What is a qualifying disposition?
A qualifying disposition means you sold the shares at least one year after exercise AND at least two years after the original grant date. This qualifies your gain for long-term capital gains rates. Selling before either threshold is a disqualifying disposition and triggers ordinary income tax on the spread.
Providers for this path
These providers operate in the Incentive Stock Options space. StrikeRates does not endorse or recommend any provider. Review each independently.
Sources
This content is for educational purposes only and does not constitute tax, legal, or investment advice. Tax laws and regulations change frequently. Consult a qualified tax professional or attorney before making decisions about your equity compensation.
Use the scenario modeler to see how Incentive Stock Options mechanics play out with your specific grant. The full app goes deeper: per-grant modeling, fund signals, and competing lender terms matched to your situation.