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Alternative minimum tax

AMT Form 1116 is a parallel calculation, not a duplicate form.

When alternative minimum tax applies, the foreign tax credit limitation may need to be recomputed using AMT income and deductions. That can produce a different allowed credit from the regular-tax calculation.

Reviewed September 5, 20262025 return guidance

What the AMT foreign tax credit does

The alternative minimum tax foreign tax credit limits the foreign tax that can offset tentative minimum tax. It is calculated with AMT concepts rather than simply copying the regular-tax foreign tax credit onto Form 6251.

A taxpayer can therefore have an allowed regular foreign tax credit, an AMT foreign tax credit calculation, and a remaining AMT liability on the same return.

Why a separate Form 1116 calculation may be needed

Alternative minimum taxable income can differ from regular taxable income because AMT adds back or adjusts certain items. Those differences may change foreign-source income, deductions allocated to it, taxable income in the denominator, and the resulting limit. The IRS instructions direct taxpayers to use a separate Form 1116 framework for AMT when required.

“Separate” means a separate computation for the same applicable income categories. It does not mean inventing another pool of foreign taxes. The workpaper should tie regular-tax and AMT inputs to the same source records.

Why tax software can show an AMT Form 1116 diagnostic

Software may ask for AMT versions of income, deductions, and carryover information even when the regular Form 1116 looks complete. Diagnostics often appear when source data is missing, a category does not reconcile, or a program cannot infer how an AMT adjustment should be allocated.

Overriding the diagnostic without tracing the input can hide the mismatch. The better approach is to identify which regular-tax item changes under AMT and follow that item through the limitation.

AMT and foreign tax credit carryovers

Regular-tax and AMT limitation histories can diverge. A carryover ledger should preserve the information needed for both calculations and each separate income category. When an older return has only a single combined number, reconstruction may be necessary before a reliable current-year result can be produced.

What to review when the AMT result seems wrong

  • Whether Form 6251 actually produces tentative minimum tax and an AMT liability.
  • Which Form 1116 categories apply under the regular and AMT calculations.
  • AMT adjustments to foreign-source income and related deductions.
  • Qualified-dividend and capital-gain worksheets.
  • Regular and AMT carryover schedules from prior years.
  • Software overrides or imported figures that no longer tie to source documents.

Primary IRS sources

Instructions for Form 1116Instructions for Form 6251Foreign Tax Credit special issues
Start with the Form 1116 guideRegular and AMT carryoversForm 1116 for investorsGet an AMT calculation reviewed