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What will you owe in AMT when you exercise your ISOs?
ISO exercise doesn’t create regular income tax, but the spread between your strike price and current FMV is an AMT preference item. For large exercises, this can mean a six-figure tax bill due in April. Model the two paths before you decide when to exercise.
2026 estimates · Federal AMT · Hold vs. sell-same-year comparison · Not tax advice
ISO/AMT exposure calculator
See your AMT exposure before you exercise.
Exercising ISOs doesn’t create regular income tax, but the spread between your strike price and the current FMV is an AMT preference item. Enter your numbers to see your tentative minimum tax and any AMT bill before you decide when to exercise.
Your ISO exercise
Hold after exercise — qualifying disposition
AMT bill at exercise
$26,141
AMT exceeds your regular income tax on this exercise. You'll owe this amount above your regular tax, due in the year you exercise.
AMT exceeds $10,000 — consider making an estimated payment
This AMT liability is due in the year you exercise. If withholding won’t cover it, an estimated quarterly payment may be required to avoid underpayment penalties. The quarter in which you exercise is the relevant deadline.
AMT credit carryforward
AMT paid in the year of exercise generally creates an AMT credit that can offset future regular tax in years when your regular tax exceeds your tentative minimum tax. This credit doesn’t expire, but it can only be used in years when you don’t owe AMT. Coordinate with your CPA on how to track and deploy this credit.
California note: California has its own AMT at approximately 7% on CA AMTI with a separate exemption. CA AMT operates independently from federal AMT. Your CPA should model both.
How the alternative minimum tax works →ISO exercise timing, AMT credit planning, and coordination between your CPA and financial advisor can determine whether this event costs you tens of thousands or nothing.
Illustrative estimates only. Uses 2026 federal income tax brackets, standard deductions, and AMT parameters. California AMT modeled separately at approximately 7% on CA AMTI (not included in totals shown). Does not model NIIT, state AMT credits, itemized deductions, or tax credits. Does not constitute tax advice. See full disclaimer.
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ReadWork with Matt
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Matt Reese, CPA coordinates ISO exercise timing, AMT exposure modeling, and AMT credit planning alongside your financial advisor, so you don't discover the bill in April.
Tax services provided through Matt Reese, CPA. This page is educational and does not constitute tax or investment advice.