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The Alternative Minimum Tax is a parallel federal income tax system in the United States that requires certain taxpayers to calculate their tax liability twice: once under regular income tax rules and once under the AMT, then pay whichever result is higher. It was created in 1969 after Congress learned that 155 high-income individuals had legally used so many deductions and credits that they paid zero federal income tax. Rather than eliminating those tax preferences, Congress created a separate system that limits their benefit, ensuring that high earners pay at least a minimum amount of tax regardless of how their deductions are structured.
The regular income tax system allows many deductions, exclusions, and credits that provide greater benefit to high-income taxpayers because those taxpayers face higher marginal rates. A deduction worth $10,000 to someone in a 12% bracket is worth $10,000 more to someone in a 37% bracket. The AMT addresses this asymmetry by computing taxable income under a different set of rules that adds back many of the items that reduce regular taxable income, then taxing the resulting Alternative Minimum Taxable Income (AMTI) at flat rates of 26% or 28%.
The calculation follows a structured sequence. Start with regular taxable income. Add back AMT adjustment items and tax preference items. Common add-backs include state and local tax deductions, the bargain element on incentive stock option exercises, interest from certain private activity municipal bonds, and some accelerated depreciation deductions. The sum of these amounts produces AMTI.
Subtract the AMT exemption, which acts like a large standard deduction for AMT purposes. For the 2025 tax year, the exemption is $88,100 for single filers and $137,000 for married couples filing jointly. The exemption phases out at a rate of 25 cents for each dollar of AMTI above specified thresholds ($626,350 for single filers in 2025), which means very high earners receive no exemption at all.
Apply the AMT tax rates to the remaining AMTI: 26% on amounts up to $232,600 and 28% on amounts above that threshold (2025 figures). Subtract the AMT foreign tax credit if applicable. Compare this tentative minimum tax to regular tax liability. If the tentative minimum tax is higher, the difference is the AMT owed, which gets added to the regular tax bill.
| Filing Status | 2025 Exemption | Phase-out Begins At |
|---|---|---|
| Single / Head of Household | $88,100 | $626,350 |
| Married Filing Jointly | $137,000 | $1,252,700 |
| Married Filing Separately | $68,500 | $626,350 |
Before the Tax Cuts and Jobs Act of 2017, approximately 5 million taxpayers faced the AMT annually. The TCJA dramatically raised exemption amounts and phaseout thresholds, reducing the affected population to roughly 200,000. The higher limits were set to expire after 2025, but the 2025 "One Big Beautiful Bill Act" made the higher exemption amounts permanent while modifying the phaseout thresholds and increasing the phase-out rate from 25% to 50% for tax years beginning in 2026.
The most frequent AMT trigger for individual taxpayers is the exercise of incentive stock options (ISOs). When an employee exercises an ISO without immediately selling the shares, the spread between the exercise price and the stock's fair market value is not taxable under regular rules but is added to income under AMT. If the stock subsequently falls in value, this can create a situation where AMT is owed on gains that have since disappeared, which created significant hardship for technology employees during the dot-com collapse.
Large state and local tax deductions (state income taxes, property taxes) are also added back under AMT, which is why taxpayers in high-tax states like California and New York are more frequently exposed to AMT even with moderate income levels.
With deep roots in traditional finance and the digital asset industry, Acquire.Fi operates as a specialist M&A advisory firm. Coverage spans M&A, secondaries, OTC, and capital markets advisory across digital assets and frontier tech. Our team has decades of combined experience across every stage of the deal lifecycle.
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