Alternative Minimum Tax (AMT) Calculator
The AMT is a parallel tax system that adds back certain deductions and preferences. The two biggest triggers are ISO stock option exercises and state/local tax deductions. This calculator shows your AMT liability and how much ISO exercise is safe.
How the AMT Works
What triggers AMT. The most common AMT triggers are: (1) exercising incentive stock options (ISOs), where the bargain element (FMV - strike price) is an AMT preference item; (2) large state and local tax (SALT) deductions that are added back for AMT purposes; and (3) certain miscellaneous deductions.
2026 AMT exemptions (OBBBA). Single: $90,100 exemption, phasing out at $500,000. MFJ: $140,200 exemption, phasing out at $1,000,000. The OBBBA doubled the phaseout rate to $0.50 per $1 over the threshold (up from $0.25), meaning the exemption is eliminated faster.
AMT rates. 26% on AMTI up to $244,500 (single) / $244,500 (MFJ), and 28% above that. Capital gains and qualified dividends are taxed at the same preferential rates under both the regular and AMT systems.
ISO exercises and AMT. When you exercise ISOs, the spread between the fair market value and your strike price is not taxed for regular income tax purposes, but it IS added to your income for AMT. A large ISO exercise can create a substantial AMT bill even though you received no cash.
AMT credit carryforward. AMT paid due to timing differences (like ISOs) generates a credit (Form 8801) that can offset regular tax in future years. When you sell the ISO stock, the AMT cost basis is higher, so you pay less capital gains tax — and you can use the AMT credit to reduce regular tax. The AMT is often a timing issue, not a permanent additional tax.
SALT cap effect. The $40,000+ SALT cap (post-OBBBA) limits the SALT deduction for regular tax purposes, which also reduces the AMT add-back. This means fewer taxpayers are affected by AMT due to SALT alone compared to pre-2018.