What the AMT is and why it matters to your tax bill

The Alternative Minimum Tax (AMT) is a separate tax calculation that runs parallel to your regular federal income tax. If your AMT comes out higher than your regular tax, you pay the AMT instead. The AMT exists because Congress wanted to may support that high-income taxpayers pay at least some minimum amount of tax, even if deductions and credits would otherwise reduce their bill to near zero.

The AMT uses its own set of rules about what you can deduct and what counts as income. Many deductions that lower your regular tax bill — like state and local taxes, mortgage interest on second homes, and miscellaneous itemized deductions — are either limited or disallowed under AMT rules. This means you can end up owing more tax than you expected, even if you followed all the normal tax-reduction strategies.

Whether you owe AMT depends on your income level, the types of deductions you claim, and the tax credits you use. The AMT exemption amount (the income level below which you do not owe AMT) changes each year and is higher for married couples filing jointly than for single filers. For 2024, the exemption is $85,975 for single filers and $133,950 for married couples filing jointly, but these figures are adjusted annually for inflation.

Key Takeaways

  • The AMT triggers when your income is high enough and you claim enough deductions that the AMT calculation produces a higher tax bill than your regular tax.
  • State and local tax deductions, mortgage interest on second homes, and incentive stock options are common triggers because they reduce regular tax but do not reduce AMT income.
  • Bunching deductions into alternate years, timing capital gains, and managing incentive stock option exercises can reduce AMT exposure.
  • Tax credits reduce your final bill under both regular tax and AMT, but some credits work differently under AMT rules.
  • A tax professional can model your AMT liability before year-end and suggest adjustments to your income and deductions.

Understand which deductions trigger AMT exposure

The first step to avoiding AMT is knowing which deductions and income items are treated differently under AMT rules. State and local taxes (SALT) — including income tax, property tax, and sales tax — are fully deductible under regular tax rules but are not deductible at all under AMT. If you live in a high-tax state and claim large SALT deductions, you are a candidate for AMT.

Mortgage interest on a primary home is deductible under both regular tax and AMT. However, mortgage interest on a second home or home equity line of credit is deductible under regular tax but not under AMT, unless the loan was used to build or improve the home. Miscellaneous itemized deductions — such as investment advisory fees, tax preparation costs, and unreimbursed employee expenses — are also disallowed under AMT.

Incentive stock options (ISOs) create AMT exposure because the spread between the exercise price and the fair market value of the stock on the exercise date counts as income for AMT purposes, even though you have not sold the stock and have no cash to pay the tax. This can create a large AMT bill in the year you exercise options, especially if the stock price is high.

Bunch deductions into alternate years

One practical strategy is to bunch deductions — accelerate some deductions into one year and defer others to the next year, so that you claim large deductions in some years and smaller ones in others. This approach works because the AMT exemption phases out as your income rises, and bunching can keep your income below the threshold in some years.

For example, if you are close to the AMT threshold, you might pay your January property tax bill in December of the prior year (if your state allows it) to claim the deduction in a year when you have lower income. In the following year, you defer discretionary deductions like charitable donations or business expenses to the next tax year. This creates a year with high deductions and a year with low deductions, potentially keeping you below the AMT threshold in both years.

Bunching works best if you have control over the timing of deductions — charitable donations, estimated tax payments, and some business expenses fall into this category. It does not work for deductions tied to a specific date, like property taxes due on a set date or mortgage interest that accrues monthly.

Time capital gains and manage stock exercises

Capital gains are taxed under both regular tax and AMT, but the timing of when you realize gains can affect whether you trigger AMT. If you are close to the AMT threshold, deferring a large capital gain to the next year may keep you below the threshold in the current year.

If you hold incentive stock options, the year you exercise them matters significantly. Exercising a large number of ISOs in a single year can create a substantial AMT liability because the spread counts as AMT income. Spreading exercises across two years, or exercising in a year when you have lower income from other sources, can reduce AMT exposure. If you exercise ISOs and the stock price later falls, you may be able to claim an AMT credit in future years, but only if you owe regular tax in those years.

Selling shares of stock acquired through an ISO exercise can also affect your AMT. If you sell the shares in the same year you exercise the option, the gain or loss on the sale may offset some of the AMT income created by the exercise. Consult a tax professional before exercising large numbers of options to model the AMT impact.

Use tax credits strategically

Tax credits reduce your tax bill dollar-for-dollar, and most credits work under both regular tax and AMT. However, some credits are treated differently under AMT rules, and some credits cannot be used to reduce AMT at all. The child tax credit, earned income tax credit, and dependent care credit generally work the same way under both systems.

If you are subject to AMT, certain credits — like the research and development credit — may be limited or unavailable. Other credits, like the energy-efficient home improvement credit, may be available under regular tax but not under AMT. Understanding which credits you can use under AMT rules helps you plan whether to claim them in a year when you owe AMT or defer them to a year when you do not.

If you pay AMT in one year, you may be able to claim an AMT credit in future years when your regular tax exceeds your AMT. This credit is not refundable, so you can only use it to reduce tax you owe in future years, not to get a refund. The mechanics of the AMT credit are complex, and a tax professional can help you track and claim it correctly.

Work with a tax professional to model your liability

The most effective way to avoid AMT is to run the numbers before the year ends. A tax professional can calculate your projected regular tax and AMT for the current year based on your income and deductions to date, then model how different decisions — like timing a bonus, deferring a capital gain, or bunching deductions — would affect your final bill.

This modeling is especially valuable if you are self-employed, exercise stock options, have significant investment income, or live in a high-tax state. A professional can also help you understand the long-term impact of AMT, because paying AMT in one year may create an AMT credit you can use in future years, which changes the true cost of the tax.

Many tax professionals offer a year-end planning call in November or December specifically to address AMT exposure. Bringing your income and deduction estimates to that call — along with any major transactions you are considering before year-end — gives the professional enough information to suggest concrete steps you can take in the remaining weeks of the year.

Consider your overall tax strategy, not just AMT

Avoiding AMT should not be your only goal. Some strategies that reduce AMT might increase your regular tax, or vice versa. For example, deferring a capital gain to avoid AMT might push you into a higher regular tax bracket in the next year. Bunching deductions might reduce your charitable giving in some years, which could affect your long-term financial plan.

A tax professional can help you weigh these trade-offs and choose strategies that reduce your total tax bill over multiple years, not just in the current year. This is especially important if you are in a transition year — such as the year you retire, sell a business, or have a large one-time gain — because your income and tax situation may change significantly in the following years.

Frequently Asked Questions

Can I avoid AMT by not taking deductions?

Not entirely. Even if you take the standard deduction instead of itemizing, you can still owe AMT if your income is high enough. However, the standard deduction is treated the same way under both regular tax and AMT, so using it does not create AMT exposure the way large itemized deductions do. If you are close to the AMT threshold, switching from itemizing to the standard deduction may help.

Does the AMT exemption phase out completely?

The AMT exemption phases out as your income rises, but it does not disappear entirely. For 2024, the exemption phases out at a rate of 25 cents for every dollar of income above the threshold. This means that even high-income taxpayers retain some exemption, though it becomes smaller as income increases.

What is an AMT credit and how do I use it?

An AMT credit is a dollar-for-dollar reduction in your regular tax in future years if you paid AMT in a prior year. You can only use the credit in years when your regular tax exceeds your AMT. The credit is not refundable, so you cannot get money back if the credit exceeds your tax bill. A tax professional can help you calculate and track your AMT credit over time.

Does exercising stock options always trigger AMT?

Exercising incentive stock options creates AMT income in the year of exercise, but whether you actually owe AMT depends on your total income and deductions that year. If your regular tax is higher than your AMT, you do not owe AMT even though the options created AMT income. However, the AMT income can push you over the threshold if your other income is already high.

Can I claim an AMT credit if I move to a lower-tax state?

Yes. If you paid AMT in a prior year partly because of state and local tax deductions, and you later move to a state with lower taxes, you may owe less AMT (or no AMT) in future years. This creates an opportunity to use your AMT credit to reduce your regular tax in those years. The credit does not expire, so you can carry it forward indefinitely until you use it.