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Alternative minimum tax for investors

The Alternative Minimum Tax (AMT) is a parallel federal tax system designed to ensure that high-income earners pay a minimum amount of tax. Taxpayers with high income or certain deductions (like large depreciation, private activity bonds, or concentrated capital gains) must calculate both regular tax and AMT, then pay whichever is higher. For affected investors, AMT can increase the effective tax rate by several percentage points.

For regular tax rates, see marginal tax rate investor. For capital gains treatment under AMT, see long-term capital gain tax.

How AMT works

You calculate tax in two ways:

Regular tax: Using standard brackets and deductions (what most people calculate).

AMT: Starting with “Alternative Minimum Taxable Income” (AMTI), which adds back certain deductions and preferences, then applies a flat 26%-28% rate.

You pay the higher of the two.

Example: regular vs. AMT

Suppose your regular taxable income is $300,000 (marginal rate 35%, tax ~$105,000).

You have $100,000 in depreciation deductions (say, from a rental property partnership via K-1 income).

For AMT, you add back the $100,000 depreciation, making AMTI = $400,000. At 28% AMT rate, AMT = $112,000.

Regular tax: $105,000. AMT: $112,000. You pay the higher: $112,000 AMT.

The $7,000 difference is the cost of AMT—it increased your tax despite the depreciation deduction.

AMTI and preferences

Alternative Minimum Taxable Income starts with regular taxable income and adds back certain “preference items”:

For investors, the big one is depreciation, especially K-1 income from real estate partnerships.

The AMT exemption

There is an exemption amount (roughly $85,925 for single filers, $133,500 for married, in 2024) that reduces AMTI before the 26%-28% rate is applied. This exemption phases out as AMTI rises, making the effective AMT rate higher for very high earners.

Long-term capital gains and AMT

Good news: long-term capital gains are taxed at preferential rates under AMT, just like regular tax. This is rare—most tax preferences are bad under AMT, but long-term gains are taxed at 0%, 15%, or 20% under both systems.

Who is affected

AMT is most common for:

Form 6251

AMT is calculated on Form 6251, filed with the return. If your calculation shows AMT higher than regular tax, Form 6251 is required; otherwise, it is optional (though recommended to track).

Your tax software will calculate it automatically if you have preference items.

AMT credit and carryforward

If you pay AMT in one year because of timing preferences (like depreciation, which creates a difference between years), you can claim an AMT credit in later years when regular tax exceeds AMT. This credit can refund some of the AMT you overpaid.

The credit is complex to calculate; most tax software handles it.

Mitigation strategies

If you are subject to AMT:

  1. Spread depreciation. If you can choose between accelerated and straight-line depreciation, straight-line may reduce AMT.
  2. Avoid preference items. Be cautious about private activity bonds or incentive stock options.
  3. Timing capital gains. AMT does not penalize long-term gains, so gains are less harmful under AMT than ordinary income.
  4. Consult a tax professional. AMT is complex; professional guidance can identify the best strategy.

Historical note

AMT was enacted to prevent high-income earners from using deductions to avoid tax entirely. However, due to a failure to index the exemption for inflation (until 2013), AMT increasingly affects middle-income taxpayers in high-tax states. The exemption is now indexed, limiting the reach.

See also

Wider context