IRS Form 6251 – The IRS requires many high-income taxpayers, investors, and people with stock options to file Form 6251 each year. This form calculates the Alternative Minimum Tax (AMT), a parallel tax system designed to ensure that individuals with significant tax preferences or deductions still pay a minimum amount of federal income tax.
The latest version of Form 6251 applies to tax year 2025 (returns filed in 2026). Download it directly from the IRS:
Form 6251 (2025) PDF
Instructions for Form 6251 (2025) PDF
What Is the Alternative Minimum Tax (AMT)?
The AMT prevents taxpayers from using certain deductions, exclusions, and credits to reduce their tax bill too much. It recalculates your taxable income under a stricter set of rules (no state and local tax deduction, no miscellaneous itemized deductions, different treatment of incentive stock options, etc.).
You pay the higher of:
- Your regular tax (Form 1040), or
- Your tentative minimum tax (calculated on Form 6251).
If the tentative minimum tax > regular tax, you owe AMT on the difference (reported on Schedule 2 of Form 1040).
Visual: How AMT is calculated (step-by-step flowchart)
Who Must File Form 6251?
You must attach Form 6251 to your return if any of these apply (per 2025 instructions):
- Line 7 (tentative minimum tax) > Line 10 (regular tax)
- You claim certain general business credits (Form 3800) and specific lines are > $0
- You claim the qualified electric vehicle credit, alternative fuel vehicle refueling property credit, or credit for prior year minimum tax
- Certain negative adjustments exist that would otherwise make line 7 > line 10
Even if you owe $0 AMT, you may still need to file the form if you have incentive stock options (ISOs), large state tax deductions, or other AMT preference items.
2025 AMT Exemption Amounts & Phaseouts
| Filing Status | Exemption Amount | Phaseout Begins At (AMTI) | Exemption Fully Phased Out At |
|---|---|---|---|
| Single / Head of Household | $88,100 | $626,350 | $978,750 |
| Married Filing Jointly / Qualifying Surviving Spouse | $137,000 | $1,252,700 | $1,800,700 |
| Married Filing Separately | $68,500 | $626,350 | $900,350 (with special rules) |
The exemption phases out by 25 cents for every dollar of AMTI above the threshold.
AMT Tax Rates (2025)
- 26% on the first $239,100 of AMT taxable excess ($119,550 if married filing separately)
- 28% on the amount above that
Common Triggers That Cause AMT
Most frequent reasons taxpayers owe AMT in 2025:
- Exercising Incentive Stock Options (ISOs) — the “bargain element” is added to AMTI
- Large state and local tax (SALT) deductions on Schedule A
- Tax-exempt interest from private activity bonds
- Depreciation differences (accelerated vs. straight-line)
- Qualified small business stock exclusions
- Large capital gains or qualified dividends (though less common after TCJA changes)
- Net operating losses or passive activity losses
How to Fill Out Form 6251 (High-Level Steps)?
Part I – Alternative Minimum Taxable Income (AMTI)
Start with your regular taxable income → add back disallowed deductions → make other adjustments.
Part II – Tentative Minimum Tax
Subtract exemption → apply 26%/28% rates → compare to regular tax.
Part III – Capital Gains Worksheet (if you have qualified dividends or long-term capital gains)
Tax software (TurboTax, H&R Block, TaxAct, etc.) usually fills this automatically and tells you if you need to file it.
Key Changes for Tax Year 2025
- Exemption amounts and phaseout thresholds increased for inflation
- New $6,000 enhanced deduction for seniors (born before Jan. 2, 1961) is added back as an AMT adjustment
- AMT tax brackets adjusted: $239,100 / $119,550 threshold
Note: The TCJA’s AMT “fix” (higher exemptions) expires after 2025. Unless Congress acts, far more middle- and upper-middle-income taxpayers could face AMT in 2026 and beyond.
How to Minimize or Avoid AMT?
- Exercise ISOs strategically (spread over multiple years)
- Pay estimated taxes early or bunch deductions
- Consider Roth conversions or other income-shifting in low-AMT years
- Use tax software’s “what-if” scenarios
Frequently Asked Questions
Do I owe AMT if my income is under $200,000?
Usually not — but ISO exercises can still trigger it.
Can I claim the standard deduction under AMT?
Yes, the standard deduction is allowed (unlike many itemized deductions).
What if I paid AMT in a prior year?
You may be eligible for a credit for prior year minimum tax (Form 8801).
Do I need to file Form 6251 every year?
Only if one of the “who must file” conditions is met or your software flags it.
Final Tip
Always run your return both ways (regular tax vs. AMT) using tax software or the IRS instructions worksheet. Even if you don’t owe AMT this year, understanding Form 6251 helps you plan for future years — especially with the potential return of broader AMT exposure after 2025.
Official IRS Resources
- About Form 6251 → https://www.irs.gov/forms-pubs/about-form-6251
- 2025 Instructions → https://www.irs.gov/instructions/i6251
- Topic No. 556 – Alternative Minimum Tax → https://www.irs.gov/taxtopics/tc556
Need help with your specific situation? Consult a tax professional or CPA familiar with AMT planning, especially if you have stock options or high state taxes.
This guide is based on official IRS publications for tax year 2025 (as of February 2026). Tax rules can change — always verify with the latest IRS forms and instructions.