Long-term capital gains keep their preferential 0%, 15%, and 20% rates under the Alternative Minimum Tax. The AMT does not reclassify a long-term gain as ordinary income or tax it at the AMT’s 26% or 28% rates. What the AMT can do is raise the income base that decides which capital gains bracket your gain lands in, so a large sale combined with other AMT add-backs can push more of your gain into the 15% or 20% rate than the regular tax would.
Long-Term Gains Keep the Preferential Rates
If you hold an asset more than one year and sell at a gain, the AMT uses the same 0%/15%/20% rate schedule the regular tax uses. For 2026, a single filer’s 15% bracket runs from $49,450 to $545,500, with 20% applying above $545,500. For married couples filing jointly, the 15% bracket runs from $98,900 to $613,700, with 20% above $613,700. The AMT applies those same breakpoints, but measures your income against them using your Alternative Minimum Taxable Income rather than regular taxable income.1Internal Revenue Service. Topic No. 556, Alternative Minimum Tax
Short-term gains get no such treatment. Assets held one year or less produce ordinary income under both systems, so the gain faces the full 26% or 28% AMT rate after your exemption is applied.2Internal Revenue Service. Instructions for Form 6251
How the Stacking Calculation Sets Your Rate
Applying preferential rates inside the AMT is not as simple as pulling gains out and taxing them at 15%. Form 6251 (Part III) uses a stacking approach. Your ordinary AMTI is figured first and taxed at the 26%/28% AMT rates. Your net long-term capital gain then stacks on top, and the preferential rate that applies to each dollar of gain depends on where the ordinary AMTI left off on the 0%/15%/20% schedule.2Internal Revenue Service. Instructions for Form 6251
An example makes this concrete. A single filer with $400,000 of ordinary AMTI and $200,000 of long-term capital gain stacks the gain on top of the $400,000. The 20% threshold for single filers is $545,500, so the first $145,500 of gain falls in the 15% bracket and the remaining $54,500 is taxed at 20%. The ordinary AMTI is taxed separately at the 26%/28% AMT rates.
The IRS requires the AMT Qualified Dividends and Capital Gain Tax Worksheet or the AMT Schedule D Tax Worksheet to run this math, and the results feed into Part III of Form 6251.
What Actually Triggers AMT for Investors
Capital gains by themselves rarely cause AMT. Because they are taxed at the same preferential rates under both systems, the gap between regular tax and tentative minimum tax comes from other adjustments. A large gain magnifies the effect of those adjustments by inflating overall AMTI, but the trigger is usually something else on the return.
State and Local Tax Deductions
Under the regular tax, the SALT deduction is capped at $40,000 for tax years 2025 through 2029 under the One, Big, Beautiful Bill, with a phaseout starting at $500,000 of household income.3Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026 For AMT purposes, the entire SALT deduction is disallowed. State income tax, local tax, and property tax all get added back into AMTI. For a resident of a high-tax state who also realizes a large gain, that add-back can lift AMTI enough to push more of the gain into the 20% capital gains bracket than the regular tax would.
Incentive Stock Options
Exercising ISOs is the largest single AMT trigger many taxpayers ever face. Under the regular tax, exercising and holding an ISO produces no income. Under the AMT, the bargain element — the spread between the exercise price and the fair market value on the exercise date — is added to AMTI as an adjustment.2Internal Revenue Service. Instructions for Form 6251 Exercise options on stock worth $200,000 for $20,000, and $180,000 flows into AMTI on paper gain you haven’t sold.
This is a timing difference, not a permanent one. Your AMT basis in the stock is higher than your regular tax basis, so the AMT gain when you sell will be smaller, and the AMT paid at exercise generates a Minimum Tax Credit against future regular tax.
Private Activity Bond Interest
Interest from private activity bonds issued after August 7, 1986 is tax-exempt for regular tax purposes but included in AMTI as a preference item. If you hold municipal bond funds, some portion of your exempt-interest dividends may be attributable to private activity bonds, so the adjustment can apply even without direct bond ownership.2Internal Revenue Service. Instructions for Form 6251
Depreciation Differences
Rental property and other depreciable business assets may generate a smaller depreciation deduction for AMT than for regular tax. AMT requires the 150% declining balance method for certain property while the regular tax allows more accelerated methods, and the difference is added back to AMTI.4Office of the Law Revision Counsel. 26 USC 56 – Adjustments in Computing Alternative Minimum Taxable Income
Track Capital Loss Carryovers Separately
You may need two capital loss carryover figures: one for regular tax and one for AMT. Cost basis can differ between the two systems (a common result of ISO exercises), so the gain or loss on a sale can differ, and any resulting loss carryover can differ too. The IRS provides an AMT Capital Loss Carryover Worksheet in the Schedule D instructions for tracking the parallel figure.5Internal Revenue Service. Instructions for Form 6251 – Alternative Minimum Tax – Individuals Errors here compound across years, so a spreadsheet or software that carries both figures forward is worth the effort.
Qualified Small Business Stock
Section 1202 lets you exclude gain on the sale of qualified small business stock held more than five years. For QSBS acquired after September 27, 2010, the full exclusion applies and none of the excluded gain is an AMT preference item. Regular tax and AMT both leave the gain alone.
Older QSBS is different. Stock issued before September 28, 2010 qualifies for only a 50% or 75% exclusion depending on acquisition date, and the excluded portion is a preference item for AMT. That excluded gain gets added back into AMTI and can trigger AMT on income you excluded from the regular tax. Because it is an exclusion preference rather than a timing difference, AMT paid on it does not produce a Minimum Tax Credit.6Internal Revenue Service. 2025 Instructions for Form 8801
The 3.8% Net Investment Income Tax
The AMT is not the only extra tax on capital gains. The Net Investment Income Tax adds 3.8% on top of the capital gains rate once modified adjusted gross income exceeds $200,000 (single) or $250,000 (married filing jointly). The NIIT is calculated separately from both the regular tax and the AMT.7Internal Revenue Service. Topic No. 559, Net Investment Income Tax
A high-income taxpayer in the 20% capital gains bracket who is also subject to the NIIT pays 23.8% on long-term gains at the federal level before any state tax. The NIIT thresholds are not indexed for inflation, so a large sale or ISO exercise planned around the AMT alone can still produce a meaningful underestimate of total tax.
Recovering AMT Through the Minimum Tax Credit
AMT paid because of timing differences is not lost. The Minimum Tax Credit tracks AMT attributable to deferral items and lets you claim it against regular tax in any later year where the regular tax exceeds the tentative minimum tax. The credit reduces regular tax down to (but not below) the tentative minimum tax and carries forward indefinitely. You calculate and claim it on Form 8801.6Internal Revenue Service. 2025 Instructions for Form 8801
Only deferral items generate the credit. The ISO bargain element and depreciation differences qualify because they eventually reverse. Exclusion items — the SALT disallowance, the standard deduction add-back, private activity bond interest, and the older Section 1202 exclusion — cause permanent differences and do not create a credit.6Internal Revenue Service. 2025 Instructions for Form 8801
For an investor who paid a large AMT bill on an ISO exercise, the credit is where the math eventually settles. When you sell the shares, your higher AMT basis produces a smaller AMT gain, regular tax typically exceeds the tentative minimum tax, and the accumulated credit becomes usable. Keep both bases on the stock from exercise through sale so the credit calculation is right when the sale year arrives.