By Harry Prabandham · Updated September 27, 2026
Equity Compensation
Timing ISO Exercises Around the Alternative Minimum Tax
Exercising ISOs creates no regular income tax, but the spread counts for AMT; knowing where AMT starts helps size and time each exercise.
Timing ISO Exercises Around the Alternative Minimum Tax
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How does exercising ISOs create a tax bill?
- Exercising an incentive stock option triggers no regular income tax, but the spread between fair market value and strike price is an AMT adjustment.
- If you hold the shares at least two years from grant and one year from exercise, the entire gain on sale can be long-term capital gain.
- Selling earlier is a disqualifying disposition, which turns the spread at exercise into ordinary income in the year of sale.
- Employers don't withhold tax on ISO exercises, so any AMT is due with your return or through estimated payments.
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Full Guide
How does exercising ISOs create a tax bill?
- Exercising an incentive stock option triggers no regular income tax, but the spread between fair market value and strike price is an AMT adjustment.
- If you hold the shares at least two years from grant and one year from exercise, the entire gain on sale can be long-term capital gain.
- Selling earlier is a disqualifying disposition, which turns the spread at exercise into ordinary income in the year of sale.
- Employers don't withhold tax on ISO exercises, so any AMT is due with your return or through estimated payments.
What is the AMT crossover point?
- You owe AMT only when your tentative minimum tax exceeds your regular tax; the gap between the two is how much ISO spread you can add first.
- That gap depends on wages, bonuses, capital gains, state taxes, and deductions, several of which the AMT disallows.
- For 2026, the AMT exemption is $90,100 single and $140,200 joint, and it phases out starting at $500,000 and $1,000,000 of AMT income.
- The 2025 tax law doubled the phase-out rate to 50 cents per dollar, so high earners may have less room than in 2025.
- AMT rates are 26% and 28%, with 28% applying above $244,500 of AMT income after the exemption in 2026.
Which exercise patterns do people commonly consider?
- Exercising up to the estimated crossover each year spreads the AMT exposure across tax years and starts holding periods gradually.
- Exercising and selling in the same year creates ordinary income on the spread but no AMT adjustment and no stock-price risk afterward.
- Exercising beyond the crossover and holding means paying AMT now in exchange for possible long-term capital gains later.
- Early exercise with an 83(b) election, when the spread is near zero, can reduce AMT exposure but puts cash into shares that may fail.
What if the stock drops after you exercise?
- AMT paid on a spread that later disappears is a real cost, and it has hit many employees after IPOs and market declines.
- Selling in the same calendar year as exercise can limit ordinary income to the actual gain on the sale, rather than the original spread.
- AMT paid on ISO exercises generally creates a credit (Form 8801) usable in later years when regular tax exceeds tentative minimum tax, which can take years.
- Lockups, blackout windows, and trading plans can prevent selling when the price moves, so plan for the shares to be stuck for a while.
Dates and limits worth checking
- Only $100,000 of ISOs, measured by grant-date value, can first become exercisable in a year; the excess is treated as nonqualified options.
- ISOs must be exercised within three months after employment ends to keep ISO treatment, and they expire no later than ten years after grant.
- For QSBS acquired after July 4, 2025, 50%, 75%, or 100% of gain can be excluded after three, four, or five years, capped at the greater of $15 million or 10x basis.
- The QSBS clock starts at exercise, and the company must meet C-corporation, active-business, and $75 million gross-asset tests.
Turning the numbers into a plan
- Projecting regular tax and AMT for the current year, with and without an exercise, shows the approximate crossover.
- Setting cash aside for federal and state tax matters, since California also has its own AMT that treats ISO spreads similarly.
- Deciding sale rules in advance, such as price levels or dates, can reduce the pull of headlines on a concentrated position.
- Revisiting the plan after each vest, tender offer, or price change keeps the numbers current.
Key takeaways
- ISO exercises are an AMT question first, and the crossover point varies by year and by household.
- 2026 brought a higher AMT exemption but a faster phase-out for high earners.
- Holding shares for favorable tax treatment adds price risk and concentration risk, which can outweigh the tax savings.
- This is educational only; Rubric does not prepare tax returns, so model any exercise with a CPA before acting.
Related Topics
Tax Planning
Alternative Minimum Tax (AMT) Planning
AMT is a parallel federal tax you pay when it exceeds regular tax. ISO exercises are the most common trigger; 2026 law changes widen its reach.
Equity CompensationISOs vs NSOs: How Stock Option Taxes Differ
NSO spreads are taxed as wages at exercise; ISO spreads skip regular tax but can trigger AMT, and qualify for long-term rates if holding periods are met.
Equity CompensationEarly Exercise and the 83(b) Election, Explained
Early exercise lets you buy unvested option shares now. An 83(b) election, due within 30 days, taxes them at today's value instead of at each vest.