AMT (Alternative Minimum Tax)

Quick Definition

The Alternative Minimum Tax (AMT) is a parallel federal income tax system that uses different rules to calculate your tax liability. You calculate your taxes under both the regular system and the AMT system, then pay whichever produces the higher tax. It was designed to prevent high-income earners from using deductions and preferences to eliminate most of their tax burden.

What It Means

The AMT was created in 1969 after Congress learned that 155 high-income taxpayers had paid zero federal income tax through extensive use of deductions. The fix was a minimum tax that adds back certain deductions and preferences, ensuring everyone pays at least something.

The original AMT was not indexed to inflation, causing it to creep down to middle-class taxpayers over decades. The Tax Cuts and Jobs Act of 2017 dramatically raised the AMT exemption, largely eliminating the AMT burden for middle-class filers. Now, the One Big Beautiful Bill Act (OBBBA) of 2025 has made further significant changes for tax year 2026: it lowered the phase-out thresholds and doubled the phase-out rate from 25% to 50%, meaningfully expanding AMT exposure for high earners and ISO exercisers.

How AMT Works: The Two-Track System

AMT Exemptions (2026)

The AMT exemption reduces the AMT tax base. For 2026, the exemption amounts increased roughly 2.7% from 2025 levels due to inflation indexing under IRS Revenue Procedure 2025-32:

The phase-out reduces the exemption by 50 cents for every dollar of AMTI above the threshold. This is the new OBBBA rate, doubled from the previous 25% rate that applied from 2018 through 2025.

What Changed in 2026 Under OBBBA

The combined effect of the lower thresholds and doubled phase-out rate creates a "bump zone" where every additional dollar of AMTI above the threshold increases the AMT base by $1.50 (the dollar itself plus 50 cents of lost exemption). Multiplied by the 26% or 28% AMT rates, the effective marginal rate inside the phase-out band is roughly 39% (26% x 1.5) or 42% (28% x 1.5).

AMT Rates (2026)

Long-term capital gains and qualified dividends retain their preferential rates under AMT. They are taxed at 0%, 15%, or 20% regardless of whether you are in the regular or AMT system.

What Triggers AMT

Common AMT "preference items" that add back to regular income:

ISO Exercise and the AMT Trap

The most common AMT trigger for employees of tech startups and public companies is exercising Incentive Stock Options (ISOs):

How it works:

• You receive ISOs with an exercise price of $5/share
• Stock is now worth $50/share
• You exercise 10,000 shares (pay $50,000 for shares worth $500,000)
• The $450,000 spread is NOT taxable income for regular tax at exercise
• But that $450,000 spread IS an AMT preference item, added to AMT income

AMT calculation on a large ISO exercise (2026, single filer):

• AMTI increases by $450,000
• Assume base AMTI was $200,000, so total AMTI = $650,000
• Phase-out reduction: ($650,000 - $500,000) x 50% = $75,000
• Exemption after phase-out: $90,100 - $75,000 = $15,100
• AMT base: $650,000 - $15,100 = $634,900
• AMT at 26%/28%: approximately $170,000+

This can create a massive unexpected tax bill, especially if the stock price falls after exercise but before sale, leaving the taxpayer with a large AMT liability on gains that have evaporated.

AMT Credit: A Silver Lining

When you pay AMT in one year, you earn an AMT credit (Form 8801) that you can use to reduce regular tax in future years when your regular tax exceeds your AMT:

• AMT paid in Year 1 (due to ISO exercise): $170,000
• In Year 2, regular tax exceeds AMT by $40,000
• AMT credit applied: -$40,000
• Remaining AMT credit carries forward

The credit is recoverable over time, but only if you have future years where regular tax exceeds AMT. This is not guaranteed, particularly for taxpayers with ongoing large ISO exercises or high state tax deductions.

Who Is Most Affected by AMT in 2026

After the OBBBA changes, AMT primarily hits:

How to Reduce AMT

Key Points to Remember

• AMT is a parallel tax system: you pay the higher of regular tax or AMT
• The 2026 OBBBA lowered phase-out thresholds to $500,000 (single) and $1,000,000 (MFJ), and doubled the phase-out rate from 25% to 50%
• The primary AMT trigger today is ISO (Incentive Stock Option) exercise. The spread is an AMT preference item.
• AMT rates are 26% and 28% on a broader income base. Inside the phase-out band, the effective marginal rate can reach 39% to 42%.
• AMT credit from paying AMT can be used in future years when regular tax exceeds AMT
• Always run AMT projections before exercising a large block of ISOs. The 2026 changes make this more important than ever.

Common Mistakes to Avoid

• Exercising ISOs without running AMT projections: The single most common AMT mistake. A $450,000 ISO spread can trigger a $170,000+ AMT bill in 2026 that you were not expecting.
• Assuming AMT only affects the ultra-wealthy: The OBBBA lowered the phase-out start to $500,000 for single filers. A tech employee with a $200,000 salary who exercises $400,000 in ISO spreads now crosses the threshold.
• Forgetting about the AMT credit: If you paid AMT in a prior year, you may have a credit carryforward on Form 8801 that can reduce your current year tax. Many taxpayers overlook this.
• Ignoring the bump zone: Inside the phase-out band, your effective marginal rate is 39% to 42%, not 26% or 28%. This affects decisions about additional income, capital gains harvesting, and Roth conversions.

Related Concepts

AMT interacts with several other tax concepts. Your tax bracket determines your regular tax rate, but AMT replaces it with a flat 26% or 28% on a broader base. Your AGI is the starting point for both calculations. The SALT tax deduction elimination under AMT hits residents of high-tax states hardest. Capital gains tax rates are preserved under AMT, but the income from gains can push you into the AMT phase-out zone. The IRS provides Form 6251 for calculating AMT and Form 8801 for tracking the AMT credit.

For further reading, check out our blog posts on how tax brackets work, standard deduction vs. itemizing, and how to do your own taxes for free. You can also use our tax bracket calculator to estimate your regular tax liability.

Frequently Asked Questions

Q: How do I know if I owe AMT? A: Complete Form 6251 (Alternative Minimum Tax: Individuals) or use tax software that calculates AMT automatically. If your tentative minimum tax exceeds your regular tax, you owe AMT for the difference. Tax software like TurboTax and FreeTaxUSA handles this calculation automatically.

Q: Can I owe AMT if I'm not in the top tax bracket? A: After the OBBBA changes, this is more possible than it was under the TCJA. Certain triggers (ISO exercises, private activity bond interest) can push someone into AMT territory even at moderate income levels if those preference items are large enough. A single filer with $150,000 salary who exercises $400,000 in ISO spreads would have AMTI of $550,000, crossing the $500,000 phase-out threshold.

Q: Is there AMT for corporations? A: The Inflation Reduction Act of 2022 instituted a 15% Corporate Alternative Minimum Tax on corporations with over $1 billion in average annual book income. This is separate from the individual AMT and applies to very large corporations only.

Q: What is the difference between the 2025 and 2026 AMT? A: The OBBBA made two major changes for 2026: it lowered the phase-out thresholds from $626,350 to $500,000 (single) and from $1,252,700 to $1,000,000 (MFJ), and it doubled the phase-out rate from 25% to 50%. The exemption amounts themselves increased slightly due to inflation indexing ($90,100 vs. $88,100 for single, $140,200 vs. $137,000 for MFJ). The net effect is that more high-income filers will be exposed to AMT in 2026 than in 2025.