Alternative Minimum Tax & Stock Options
The parallel tax system that punishes ISO holders who exercise and hold.
- What triggers AMT
- ISO exercise-and-hold (spread is AMT adjustment)
- 2026 exemption (single)
- $90,100
- 2026 phase-out starts
- $500,000 AMTI
- AMT rates
- 26% up to threshold; 28% above
- Credit recovery
- IRC Section 53 carryforward (Form 8801)
- California AMT
- Separate state AMT at 7% on the spread
How the AMT works
The AMT is a parallel federal income tax system. You calculate your tax liability twice, once under the regular system and once under the AMT system, and pay whichever is higher. For ISO holders, the critical difference is that the regular tax system ignores the spread at exercise, but the AMT system adds it back as an 'adjustment.' This means exercising ISOs and holding the shares can create a large tax bill even though you received no cash and can't sell the shares.
The numbers: a realistic example
You exercise 10,000 ISOs with a $2 strike price when the 409A FMV is $14. Cash paid to exercise: $20,000. The spread is $120,000 ($12 x 10,000 shares). Under the regular tax system, no federal income tax is owed at exercise. Under the AMT system, that $120,000 is added to your Alternative Minimum Taxable Income. If your base salary is $200,000, your AMTI becomes $320,000. After applying the 2026 single-filer exemption of $90,100, your taxable AMT base is $229,900 at the 26% rate, producing a tentative minimum tax of roughly $59,774. If your regular tax on $200,000 is about $45,000, the AMT liability from the exercise is approximately $14,774. California adds its own AMT at 7% on the $120,000 spread, adding another $8,400. Total tax bill on shares you can't sell: over $23,000.
The AMT credit carryforward
When you pay AMT specifically because of an ISO exercise, the IRS treats it as a prepayment. Under IRC Section 53, you receive an AMT credit that carries forward indefinitely. You can claim this credit in any future year where your regular tax exceeds your tentative minimum tax. The credit is tracked on Form 8801. The catch: if your income stays high or you never generate a regular-tax surplus, the credit can sit unused for years or even decades. If you later qualify for a 100% QSBS exclusion on those same shares, your regular tax drops to zero, and the AMT credit becomes permanently unrecoverable.
California's separate AMT regime
California does not simply conform to the federal AMT. The state runs its own parallel AMT calculation. ISO exercises trigger a California AMT adjustment, and the state's AMT rate is a flat 7%. California also disallows the SALT deduction for AMT purposes, which can increase the state-level AMT bite. California allows its own AMT credit carryforward, tracked on separate state forms (Schedule P, FTB 3510). Bottom line: a large ISO exercise can hit you with both a federal AMT bill and a California AMT bill simultaneously.
2026 AMT threshold changes
The One Big Beautiful Bill Act permanently extended elevated AMT exemption amounts but compressed the phase-out thresholds and accelerated the phase-out rate. For 2026, the phase-out rate increases to $0.50 for every dollar of AMTI over the threshold, meaning exemptions deplete much faster than under prior law. For single filers, the exemption phase-out starts at $500,000 AMTI (down from $626,350 in 2025) and fully phases out at $680,200. For married filing jointly, the phase-out starts at $1,000,000 (down from $1,252,700 in 2025). Employees with high base salaries plus a large ISO exercise can lose the exemption entirely.
Common mistakes
Exercising a large ISO block late in the year without enough time to sell in the same calendar year to offset the AMT. Assuming the AMT credit will be recovered quickly when in reality it requires a regular-tax surplus to use. Failing to track AMT basis vs regular basis, leading to incorrect capital gains reporting on eventual sale. Ignoring California's separate AMT entirely. Not making estimated tax payments after a large exercise, triggering underpayment penalties from both the IRS and the California Franchise Tax Board.
Common questions
Can I avoid AMT entirely on ISOs?
If you exercise and sell in the same calendar year (a disqualifying disposition), the AMT adjustment disappears because the spread is taxed as ordinary income instead. You lose the ISO tax advantage but avoid the AMT. The other approach is to exercise in small batches across multiple years, keeping your AMTI below the exemption phase-out threshold each year.
Does AMT apply to NSOs?
No. NSOs are taxed as ordinary income at exercise under the regular tax system, so there is no AMT adjustment. AMT on stock options is an ISO-specific problem.
What if the stock price drops after I exercise and pay AMT?
You still owe the AMT from the exercise year, calculated on the spread at the time of exercise. If the share price later drops below your exercise price, you paid taxes on paper gains that no longer exist. This is the 'AMT trap.' The AMT credit carryforward can help recover some of this in future years, but only if your regular tax exceeds your tentative minimum tax.
How do I estimate my AMT before exercising?
Calculate your AMTI by adding the ISO spread to your regular taxable income, then apply the current exemption and rates. The IRS provides Form 6251 and instructions. For California, use Schedule P. Many tax professionals and equity planning tools can model this for you. StrikeRates' equity modeler can help you estimate the cost before you commit.
Sources
Use the scenario modeler to see how Alternative Minimum Tax & 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.