Alternative Minimum Tax Calculator

A comprehensive, step-by-step resource for understanding, calculating, and navigating the Alternative Minimum Tax system during the 2025 and 2026 tax years.

What Is the Alternative Minimum Tax?

The Alternative Minimum Tax (AMT) is a parallel tax calculation system enacted in 1969 to ensure that high-income individuals, corporations, estates, and trusts pay at least a minimum amount of federal income tax, regardless of deductions, credits, or exclusions they claim under the regular tax system.

Historical Context

Originally created when Congress discovered that 155 wealthy taxpayers legally paid zero federal income tax in 1969, the AMT was designed to close loopholes that allowed excessive use of tax preferences. While initially targeting the ultra-wealthy, the AMT began affecting middle-income taxpayers because it wasn’t indexed for inflation until 2013.

Current Impact

Following the Tax Cuts and Jobs Act (TCJA) of 2017 and the One Big Beautiful Bill Act (OBBBA) of 2025, the AMT now primarily affects:

• Taxpayers with annual incomes exceeding $500,000
• Those exercising Incentive Stock Options (ISOs)
• Residents of high-tax states with substantial state and local tax deductions
• Individuals with certain tax-exempt income from private activity bonds

Key Principle: You calculate your taxes twice—once under regular tax rules and once under AMT rules—and pay whichever amount is higher.

How AMT Is Calculated

The Core Formula

The AMT calculation follows this sequence, as detailed on IRS Form 6251:

1. Start with: Adjusted Gross Income (AGI) from Form 1040, Line 11
2. Add back: Tax preference items and AMT adjustments
3. Equals: Alternative Minimum Taxable Income (AMTI)
4. Subtract: AMT exemption amount (based on filing status and income)
5. Equals: AMT tax base
6. Multiply by: AMT tax rate (26% or 28%)
7. Equals: Tentative Minimum Tax (TMT)
8. Compare: If TMT > Regular Tax, you owe AMT

Visual Representation

Regular Taxable Income

+ Standard Deduction (added back)

+ State and Local Taxes (added back)

+ ISO Bargain Element

+ Private Activity Bond Interest

+ Other Adjustments

= Alternative Minimum Taxable Income (AMTI)

– AMT Exemption

= AMT Tax Base

× AMT Tax Rate (26% or 28%)

= Tentative Minimum Tax

If TMT > Regular Tax → Pay TMT

If TMT ≤ Regular Tax → Pay Regular Tax (no AMT)

2025 Tax Year Data (Filing in 2026)

Source: IRS Revenue Procedure 2024-40

AMT Exemption Amounts for 2025

Phase-Out Mechanics: For every dollar of AMTI above the threshold, your exemption decreases by $0.25. This continues until the exemption reaches zero.

Example: A single filer with $700,000 AMTI exceeds the threshold by $73,650 ($700,000 – $626,350). The exemption reduces by $18,412.50 (25% × $73,650), leaving an exemption of $69,687.50 ($88,100 – $18,412.50).

AMT Tax Rates for 2025

Source: Tax Foundation, IRS Revenue Procedure 2024-40

Standard Deduction for 2025

These amounts are added back for AMT purposes:

Source: IRS Revenue Procedure 2024-40, as adjusted by OBBBA

2026 Tax Year Changes Under OBBBA

Source: IRS Revenue Procedure 2025-32, Tax Foundation

On July 4, 2025, the One Big Beautiful Bill Act (OBBBA) permanently extended the TCJA’s AMT provisions with significant modifications that take effect for the 2026 tax year.

AMT Exemption Amounts for 2026

Source: IRS Revenue Procedure 2025-32

Critical Changes for 2026

1. Lower Phase-Out Thresholds

The phase-out now begins at income levels comparable to 2018:

• Single filers: Drops from $626,350 (2025) to $500,000 (2026)
• Joint filers: Drops from $1,252,700 (2025) to $1,000,000 (2026)

2. Accelerated Phase-Out Rate

The exemption phases out twice as fast in 2026:

• 2025: 25 cents per dollar
• 2026: 50 cents per dollar

3. Impact Analysis

Taxpayers with AMTI between $500,000 and $1,000,000 are significantly more likely to owe AMT in 2026 compared to 2025, even though the base exemption increased slightly.

2026 AMT Tax Rates

Source: IRS Revenue Procedure 2025-32

Comparative Example: 2025 vs. 2026

Married couple with $1,100,000 AMTI:

2025 Calculation:

• Exemption: $137,000 (full amount, as income is below $1,252,700 threshold)
• AMT Base: $963,000
• Tax: Approximately $250,240

2026 Calculation:

• Income exceeds threshold by: $100,000 ($1,100,000 – $1,000,000)
• Exemption reduction: $50,000 (50% × $100,000)
• Exemption: $90,200 ($140,200 – $50,000)
• AMT Base: $1,009,800
• Tax: Approximately $262,480

Result: The couple pays approximately $12,240 more in AMT in 2026 despite the slightly higher base exemption.

Source: Porte Brown LLC analysis, September 2025

Common AMT Triggers

Primary Triggers

1. Incentive Stock Options (ISOs)

The “bargain element”—the difference between the exercise price and fair market value at exercise—is taxable for AMT purposes even if you haven’t sold the stock.

Example: You exercise ISOs with a strike price of $10 per share when the fair market value is $50 per share for 10,000 shares.

• Bargain element: ($50 – $10) × 10,000 = $400,000
• This $400,000 is added to your AMTI, potentially triggering substantial AMT liability.

Source: Carta.com, Bankrate

2. State and Local Taxes (SALT)

While SALT deductions are capped at $10,000 for regular tax (increased to $40,000 for 2025-2029 under OBBBA), they are completely disallowed for AMT purposes.

2025-2029 SALT Changes Under OBBBA:

• Deduction increases to $40,000 ($20,000 for MFS) for tax years 2025-2029
• Phases down by 30% for MAGI between $500,000-$600,000
• Reverts to $10,000 in 2030 unless extended
• Still disallowed for AMT

Source: Charles Schwab, Baker Tilly, H&R Block

3. Standard Deduction

Under AMT rules, you cannot claim the standard deduction. The entire amount is added back to taxable income when calculating AMTI.

4. Private Activity Bond Interest

Interest from certain private activity municipal bonds is tax-free for regular tax but fully taxable for AMT purposes.

Secondary Triggers

• Accelerated depreciation on certain property
• Depletion deductions in excess of basis
• Passive activity losses from certain investments
• Long-term contracts not using percentage-of-completion method
• Net operating loss deductions (limited for AMT)

Source: IRS Form 6251 Instructions, TurboTax

Calculation Examples

Example 1: Single Filer with ISOs (2025 Tax Year)

Scenario:

• Filing Status: Single
• AGI: $200,000
• ISO Bargain Element: $50,000
• Standard Deduction: $15,750
• Regular Tax Owed: $45,000

Step 1: Calculate AMTI

AGI                           $200,000

+ ISO Bargain Element        +$50,000

+ Standard Deduction         +$15,750

= AMTI                       $265,750

Step 2: Apply Exemption

• AMTI ($265,750) < Phase-out threshold ($626,350)
• Full exemption applies: $88,100

AMTI                         $265,750

– Exemption                  -$88,100

= AMT Tax Base              $177,650

Step 3: Calculate Tentative Minimum Tax

• Base ($177,650) < $239,100, so use 26% rate

$177,650 × 0.26 = $46,189 (TMT)

Step 4: Compare and Determine AMT

Tentative Minimum Tax         $46,189

Regular Tax                   $45,000

AMT Owed                      $1,189

Total Tax Liability: $46,189

Example 2: Married Couple with High SALT (2025 Tax Year)

Scenario:

• Filing Status: Married Filing Jointly
• AGI: $400,000
• State and Local Taxes Paid: $60,000
• SALT Deduction (Regular Tax): $40,000 (under OBBBA increase)
• SALT Deduction (AMT): $0
• Itemized Deductions: $70,000
• Regular Tax Owed: $75,000

Step 1: Calculate AMTI

Taxable Income (AGI – Itemized)  $330,000

+ SALT Add-Back                  +$60,000

= AMTI                          $390,000

Step 2: Apply Exemption

• AMTI ($390,000) < Phase-out threshold ($1,252,700)
• Full exemption applies: $137,000

AMTI                         $390,000

– Exemption                 -$137,000

= AMT Tax Base              $253,000

Step 3: Calculate Tentative Minimum Tax

• First $239,100 at 26%: $62,166
• Remaining $13,900 at 28%: $3,892

$62,166 + $3,892 = $66,058 (TMT)

Step 4: Compare and Determine AMT

Tentative Minimum Tax         $66,058

Regular Tax                   $75,000

AMT Owed                         $0

Result: No AMT owed; regular tax is higher.

Example 3: High-Income Couple with Phase-Out (2026 Tax Year)

Scenario:

• Filing Status: Married Filing Jointly
• AMTI: $1,200,000
• Regular Tax: $300,000

Step 1: Calculate Reduced Exemption

AMTI                        $1,200,000

– Phase-out threshold      -$1,000,000

= Excess                      $200,000

Exemption reduction = $200,000 × 50% = $100,000

Base exemption              $140,200

– Reduction                -$100,000

= Adjusted exemption        $40,200

Step 2: Calculate AMT Tax Base

AMTI                      $1,200,000

– Adjusted exemption        -$40,200

= AMT Tax Base           $1,159,800

Step 3: Calculate Tentative Minimum Tax

First $244,500 at 26%        $63,570

Remaining $915,300 at 28%   $256,284

= TMT                       $319,854

Step 4: Compare and Determine AMT

Tentative Minimum Tax       $319,854

Regular Tax                 $300,000

AMT Owed                    $19,854

Total Tax Liability: $319,854

This demonstrates how the 2026 phase-out changes significantly increase AMT exposure for high-income taxpayers.

Avoidance Strategies

1. Manage ISO Exercises

Timing Strategies:

• Exercise ISOs early in the year to monitor AMT impact throughout the year
• Spread exercises across multiple tax years to stay below exemption thresholds
• Consider disqualifying dispositions in years when AMT is triggered
• For 2025: Exercise more ISOs before 2026’s stricter phase-out rules take effect

Source: Kitces.com, Bankrate

2. Optimize Income Timing

Deferral Techniques:

• Maximize pre-tax retirement contributions (401(k), 403(b), 457 plans)
• Contribute to Health Savings Accounts (HSAs)
• Use Flexible Spending Accounts (FSAs) where applicable
• Defer bonuses or other variable compensation when approaching AMT territory

3. Strategic Tax Planning Around SALT

2025-2029 Considerations:

• Take advantage of the $40,000 SALT deduction if not subject to AMT
• Avoid prepaying state taxes if you’re in AMT zone (it provides no benefit)
• Consider Pass-Through Entity Tax (PTET) elections in eligible states
• Be aware that SALT is still fully disallowed for AMT despite the increased regular tax deduction

Source: Baker Tilly, Charles Schwab

4. Tax Loss Harvesting

• Realize capital losses to offset capital gains
• Reduces overall AGI and AMTI
• Can carry forward unused losses to future years

5. Review Investment Holdings

• Identify and consider selling private activity bonds if AMT-prone
• Replace with investments that don’t trigger AMT preference items
• Evaluate cost-benefit of tax-exempt vs. taxable investments

6. Consider AMT Credit (Form 8801)

If you paid AMT in prior years due to “deferral items” (like ISOs), you may be eligible for a Minimum Tax Credit in future years when:

• You’re no longer subject to AMT, AND
• Your regular tax exceeds your tentative minimum tax

Source: IRS Instructions for Form 8801

Frequently Asked Questions

Who is most likely to pay AMT?

High-income taxpayers with these characteristics:

• Annual income between $500,000 and $2,000,000
• Exercising substantial ISOs
• Living in high-tax states (CA, NY, NJ, CT, IL)
• Significant private activity bond interest

Source: Tax Foundation, Bankrate

How do I know if I’m subject to AMT?

You must complete IRS Form 6251 or use tax preparation software that automatically calculates both systems. Most modern tax software (TurboTax, H&R Block, TaxAct) includes this calculation automatically.

What is Form 6251?

Form 6251 (Alternative Minimum Tax – Individuals) is the IRS form used to calculate your AMT liability. It walks through all adjustments and preferences to determine if you owe AMT.

Filing Requirements:

• Attach to Form 1040 or 1040-SR
• Due by April 15, 2026 for 2025 taxes (or October 15, 2026 with extension)
• File electronically along with your main return

Source: IRS Form 6251, SmartAsset

Can I avoid AMT completely?

While complete avoidance is difficult for high-income earners with certain income types, you can minimize exposure through:

• Strategic income and deduction timing
• Careful ISO exercise planning
• Maximing retirement contributions
• Multi-year tax planning

What happens if I paid AMT in previous years?

You may be eligible for a Minimum Tax Credit using Form 8801. This credit can offset future regular tax liability in years when you’re not subject to AMT. The credit generally applies only to “deferral” preference items (like ISOs), not “exclusion” items (like SALT or standard deduction).

Source: IRS Form 8801 Instructions

Do capital gains count toward AMT?

Yes, capital gains are included in AMTI, but they’re generally taxed at the same preferential rates (0%, 15%, or 20%) under both the regular tax system and AMT. However, the AMT can indirectly affect capital gains taxation by reducing your available exemption amount.

What is the “$600 rule” and does it affect AMT?

The “$600 rule” refers to third-party payment network reporting requirements (Form 1099-K). While unrelated to AMT triggers, any income reported via 1099-K increases your AGI, which is the starting point for AMTI calculations.

Current Status: The OBBBA modified the strict $600 threshold, implementing a phased approach with higher thresholds for casual sellers.

Source: IRS, H&R Block

Additional Resources

Official IRS Resources

• IRS Form 6251: Download PDF
• Form 6251 Instructions: Download PDF
• IRS Revenue Procedure 2024-40: 2025 inflation adjustments
• IRS Revenue Procedure 2025-32: 2026 inflation adjustments
• Form 8801: Credit for Prior Year Minimum Tax

Legislative References

• Tax Cuts and Jobs Act (TCJA) – P.L. 115-97 (December 2017)
• One Big Beautiful Bill Act (OBBBA) – P.L. 119-21 (July 4, 2025)

Important Disclaimers

Tax Law Complexity: The information provided in this guide is for educational purposes only and should not be considered professional tax advice. Tax laws are complex and frequently change. Individual circumstances vary significantly.

Seek Professional Advice: Always consult with a qualified tax professional, CPA, or tax attorney for advice specific to your situation, especially if:

• You have substantial ISO exercises
• Your income exceeds $500,000
• You’re considering complex tax strategies
• You have international income or investments

Accuracy and Updates: While every effort has been made to ensure accuracy, tax laws and IRS guidance continue to evolve. The IRS typically releases final forms and instructions in late fall for the upcoming tax year.

Not Legal or Financial Advice: This guide does not constitute legal, financial, investment, or accounting advice. Readers should not act upon this information without seeking professional counsel.

Glossary of Key Terms

Adjusted Gross Income (AGI): Total income minus specific deductions, calculated on Form 1040.

Alternative Minimum Taxable Income (AMTI): Your income as calculated under AMT rules, including add-backs of preference items.

Bargain Element: For ISOs, the difference between the exercise price and fair market value at exercise.

Incentive Stock Options (ISOs): Employee stock options with special tax treatment that can trigger AMT.

Phase-Out: The gradual reduction of the AMT exemption as income increases beyond specified thresholds.

Preference Items: Income and deductions that receive favorable treatment under regular tax but are adjusted for AMT.

Private Activity Bonds: Municipal bonds whose interest is tax-free for regular tax but taxable for AMT.

SALT (State and Local Taxes): State and local income, property, and sales taxes.

Tentative Minimum Tax (TMT): Your tax liability calculated under AMT rules before comparison with regular tax.