Form 6251

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Form 6251 (Alternative Minimum Tax — Individuals)

Form 6251 is the IRS form used to determine whether a taxpayer owes the alternative minimum tax (AMT) instead of the regular federal income tax. The AMT is a parallel tax calculation intended to limit certain deductions and ensure that higher‑income taxpayers pay a minimum level of tax.

Key points

  • Form 6251 calculates AMT liability; you pay the higher of your regular tax or the AMT.
  • The AMT disallows or limits some itemized deductions (for example, state and local tax deductions) and prevents taking the standard deduction when AMT applies.
  • AMT rates are simpler than regular brackets: generally 26% or 28%.
  • AMT exemption amounts are indexed for inflation and change yearly.

2024–2025 AMT exemptions and phase‑outs (examples)

  • 2024 exemptions:
  • Single: $85,700
  • Married filing jointly: $133,300
  • Phase‑out begins (2024): about $578,150 (single) and $1,156,300 (married filing jointly)
  • 2025 examples:
  • Single: $88,100 (exemption)
  • Married filing jointly: $137,000 (exemption)
  • Phase‑out thresholds (2025): about $626,350 (single) and $1,252,700 (married filing jointly)

(Confirm the current year’s exact amounts on the IRS website before filing, since these figures are adjusted annually.)

How AMT is calculated and how to file

  1. Compute your tax under the regular tax system (Form 1040).
  2. Compute AMT using Form 6251, which recalculates income and disallows or limits certain deductions and preferences.
  3. Compare the two taxes and pay the higher amount.
  4. Form 1040 includes a basic worksheet for AMT, but Form 6251 provides the detailed calculation. Many taxpayers use tax software or a tax professional to complete Form 6251 accurately.
  5. Some other tax forms have AMT-specific versions (for example, an AMT version of Form 1116). Only attach AMT versions when the instructions require it.

Who may be subject to the AMT

Taxpayers with higher incomes, certain types of preferential income, or substantial itemized deductions (especially disallowed items under AMT rules) are most likely to need Form 6251. If your income exceeds the AMT exemption after adjustments, you may owe AMT.

Historical context and special considerations

  • The AMT was enacted in 1969 to ensure wealthy taxpayers paid a minimum tax despite deductions and preferences.
  • Lack of inflation indexing once caused the AMT to affect many more taxpayers than intended; Congress later indexed exemption levels to inflation.
  • The Tax Cuts and Jobs Act (TCJA) of 2017 raised AMT exemptions and changed phase‑out levels, substantially reducing the number of taxpayers subject to AMT.
  • Revenue collected from the individual AMT fell sharply after TCJA (for example, from roughly $36.2 billion in 2017 to about $4.7 billion in 2019).

How common is AMT liability?

Estimates indicate a very small share of households pay AMT in recent years (for example, roughly 0.1% in 2022). If TCJA provisions that affect AMT are not extended or changed in future tax law, the number of households subject to AMT could rise.

Bottom line

Form 6251 determines whether you owe the alternative minimum tax by recalculating taxable income under AMT rules and comparing that tax to your regular tax. Because AMT rules and exemption thresholds change annually, check the current IRS instructions or consult a tax professional or reliable tax software to determine whether you must file Form 6251 and whether AMT applies to your return.

For the current form and official instructions, refer to the IRS website.