United States
Hong KongThe alternative minimum tax, and who still pays it
A parallel tax calculation that adds back certain deductions and preference items, applies an exemption and its own rates, and requires you to pay the higher of it and the regular tax. Exercising incentive stock options is the classic trigger.
A second tax system running alongside the first, and you pay whichever produces more.
The mechanism
- Start from regular taxable income.
- Add back adjustments and preference items.
- Subtract the AMT exemption, which phases out at higher incomes.
- Apply the AMT rates to the result.
- Compare with the regular tax and pay the higher.
Two rate tiers apply above the exemption, both below the top ordinary rate. AMT is not punitive in its rates; it is punitive in what it disallows.
What gets added back
- State and local tax deductions.
- The bargain element on exercising an incentive stock option, without a sale.
- Certain private activity municipal bond interest.
- Some depreciation differences.
- Certain depletion and intangible drilling costs.
The state and local tax add-back was historically the largest driver, which is why AMT exposure has always been higher in high-tax states.
The incentive stock option case
This is the scenario the exam uses, and it is a genuine planning trap.
Exercising an ISO and holding the shares creates no regular taxable income. The bargain element - the difference between the exercise price and the market value - is an AMT preference item, so it can generate a substantial tax bill on a gain that has not been realized in cash.
An employee who exercised in one year and watched the shares collapse before selling can owe AMT on a gain that no longer exists. That happened at scale after the dot-com bust and it is why the exercise-and-hold decision needs modeling before it is made.
The AMT credit
AMT paid because of timing differences - such as the ISO bargain element - generates a credit carried forward and usable in later years when regular tax exceeds tentative minimum tax.
AMT arising from exclusion items, such as disallowed state tax deductions, does not generate a credit. That distinction is examinable and frequently missed.
Planning around it
Model before acting on anything involving ISOs. Consider exercising in tranches across tax years to stay under the crossover point. Consider a same-day sale, which converts the transaction to ordinary income and removes the AMT issue entirely - at the cost of the favorable long-term treatment.
And check whether a client near the threshold should accelerate or defer deductions, since a deduction disallowed for AMT purposes is worth nothing in an AMT year.
Dollar limits and rate thresholds here are indexed annually and several were changed by the 2025 reconciliation act. Confirm the current figure against the IRS before relying on it.
Common questions
How does the alternative minimum tax work?
It is a parallel calculation: start from taxable income, add back adjustments and preference items, subtract an exemption that phases out, apply AMT rates, and pay the higher of the two taxes.
What triggers AMT?
Historically large state and local tax deductions, and the bargain element on exercising incentive stock options without selling. Certain private activity municipal interest and depreciation differences also feature.
Why are incentive stock options a problem?
Exercising and holding creates no regular taxable income but the bargain element is an AMT preference item, producing a cash tax bill on an unrealized gain.
What is the AMT credit?
A carryforward generated by AMT arising from timing differences such as the ISO bargain element, usable in later years. AMT from exclusion items such as disallowed state tax deductions generates no credit.
How do you plan around it?
Model before exercising, consider spreading exercises across tax years to stay below the crossover, or use a same-day sale - which removes the AMT issue at the cost of favorable long-term treatment.