Exercising Incentive Stock Options (ISOs) creates a "bargain element" that triggers Alternative Minimum Tax. This calculator estimates the net AMT owed on top of your regular tax.
Estimated AMT owed (above regular tax)
—
Exercise cost (cash needed)
—
Bargain element
—
AMT exemption (after phase-out)
—
AMTable income
—
AMT (parallel tax)
—
Regular tax (federal)
—
Your breakdown
Updates live as you type| Step | Amount |
|---|
The phantom income regular tax ignores
When you exercise an incentive stock option and hold the shares, regular federal income tax sees nothing happen. You paid the strike price, you got stock, no taxable event. The Alternative Minimum Tax sees something else entirely. The gap between the fair market value at exercise and the strike price you paid, called the bargain element, counts as income for AMT purposes even though no cash changed hands and you sold nothing. This is why people describe ISO exercise as phantom income. You can owe a real tax bill on a paper gain, and if the stock later falls, that bill does not go away on its own. This calculator estimates the AMT you would owe on top of your regular tax so the exercise does not blindside you in April.
How the parallel tax is built
AMT runs as a separate calculation alongside your regular tax, and you pay whichever is higher. It starts from taxable income plus the ISO bargain element, then subtracts an exemption. For 2026 the exemption is $90,100 for single and head-of-household filers, $140,200 for married filing jointly, and $70,100 for married filing separately. Phase-out starts at $500,000 of AMTI for unmarried and MFS filers and $1,000,000 for joint filers. The AMT base is taxed at 26% up to $244,500, then 28%; the MFS breakpoint is $122,250.
Exercising 5,000 options at a $23 spread
Take a single filer with $200,000 of taxable income who exercises 5,000 ISOs. The strike price is $2 and the shares are worth $25 at exercise, a spread of $23 a share. They hold the stock, so regular tax ignores the exercise, but AMT does not.
The $115,000 bargain element raises AMTI to $315,000. After the $90,100 exemption, the $224,900 AMT base produces $58,474 of tentative AMT. Regular tax on $200,000 of taxable income is $40,598, leaving about $17,876 of additional AMT, even though only $10,000 of cash left the bank and no shares were sold.
Getting the AMT back later
AMT attributable to an ISO timing adjustment may generate a minimum tax credit tracked on Form 8801. The recoverable credit is determined under the Form 8801 rules and is not necessarily every dollar of AMT paid. The cash-flow issue remains: this example requires roughly $27,876 for the exercise cost and estimated additional AMT before any later credit recovery.
How long must I hold ISO shares for the tax break?
To get the favorable long-term capital gains treatment that makes ISOs worthwhile, you must hold the shares at least two years from the grant date and at least one year from the exercise date. Meet both and your entire gain over the strike price is taxed at long-term capital gains rates when you sell, a qualifying disposition. Sell before either deadline and you have a disqualifying disposition: the bargain element becomes ordinary income on your W-2, you lose the preferential rate, but you also generally avoid the AMT problem because the income is recognized normally. Holding to qualify is what creates the AMT timing gap in the first place.
Where do I find the cash to exercise and pay the AMT?
This is the hardest practical problem with ISOs, especially at private companies where you cannot simply sell shares to raise cash. In the example, exercising costs $10,000 and the estimated additional AMT is $17,876, so you need about $27,876 of cash for stock you cannot yet sell. Model the exercise before you act and size it to cash you actually have.
What happens to my AMT if the stock crashes after I exercise?
This is the nightmare scenario that ruined many employees after the dot-com bust. If you exercise and hold, you owe AMT on the bargain element at exercise, and if the share price then collapses, the bill is still calculated on the high value at exercise, so you can owe tax on a gain that has evaporated. Selling the shares in the same calendar year you exercised turns it into a disqualifying disposition and eliminates the AMT preference, the usual escape hatch if the stock drops before year end. Once you cross into a new tax year you are largely stuck with the bill, though the resulting capital loss and the AMT credit provide partial relief over time.