Understanding the Alternative Minimum Tax (AMT)

What is the AMT and Why Does It Exist?

The Alternative Minimum Tax, or AMT, is a parallel tax system that runs alongside the regular federal income tax. It was introduced in 1969 to prevent high-income taxpayers from using deductions and credits to eliminate their tax liability entirely. Over the decades, the AMT applied to an increasing share of middle-to-upper-income taxpayers because the AMT was not indexed to inflation, even as regular tax brackets were. Recent legislation, including the One Big Beautiful Bill Act of 2025, has significantly increased AMT exemptions, reducing the number of taxpayers subject to it. However, AMT still applies to a meaningful portion of high-income earners — particularly those with high incomes, large state and local tax (SALT) deductions, and those exercising incentive stock options.

How AMT Works: Two Tax Calculations

The basic mechanics of AMT are straightforward: you calculate your taxes two ways.

Regular tax: You calculate your federal income tax the normal way, using the standard deductions, credits, and deductions you’re familiar with.

AMT: You recalculate your income using a different set of rules. The AMT has its own exemption amount, its own tax rates, and its own adjustments and preferences. Certain deductions allowed in regular tax are disallowed or limited in the AMT calculation. Certain types of income are treated differently. The result is an “alternative minimum taxable income” (AMTI).

You pay the higher of the two. If your regular tax is higher, you pay regular tax. If your AMT is higher, you pay AMT instead. Either way, you owe the larger amount.

The Two Most Common AMT Triggers

The AMT tax code contains many adjustments and preferences that distinguish it from regular tax. While there are numerous potential AMT triggers, the two most common are:

1. Exercising Incentive Stock Options (ISOs)

When you exercise an ISO, the bargain element — the difference between the fair market value and the strike price on the exercise date — is added to your AMTI, even though you don’t recognize it as regular income. This AMT adjustment can push your AMTI well above your regular taxable income, triggering AMT liability.

2. High State and Local Tax (SALT) Deductions

In the AMT calculation, the deduction for state and local income taxes is disallowed entirely. If you live in a high-income-tax state like California, New York, or New Jersey — or any state with high property taxes — the SALT add-back can substantially increase your AMTI, potentially pushing you to be subject to AMT even if your regular tax is moderate.

For high earners in these states with significant other income, bonuses, or capital gains, the SALT add-back alone can trigger substantial AMT.

The AMT Credit: What Can Be Recovered

If you pay AMT in a given year, you don’t simply lose that money. The law allows you to claim an AMT credit in future years. The credit is claimed on Form 8801 and carried forward indefinitely.

However, a critical distinction determines whether your AMT can actually be recovered: the AMT code distinguishes between adjustments and preferences, and only adjustments generate recoverable credits.

ISO Bargain Element (Adjustment): Potentially Recoverable

The ISO bargain element is treated as an AMT adjustment — a timing difference. When you exercise an ISO and pay AMT because of the bargain element, that AMT generates a credit that you can carry forward. In future years, you can recover that credit — but only to the extent that your regular tax exceeds your AMT in that year. You may recover the full credit in a single year, or you may recover it gradually across multiple years as your tax situation changes. If your accumulated credit is large and the excess of regular tax over AMT in a given year is small, you may only claim a small portion of the credit that year.

SALT Deduction (Preference): Not Recoverable

The SALT disallowance is treated as a preference — a permanent difference, not a timing difference. If you pay AMT because of the SALT add-back, that AMT does NOT generate a credit you can recover. It’s simply lost. You cannot recover it in any future year, no matter what happens to your income or tax situation.

This distinction is critical: if you’re in a high-tax state and your AMT is driven primarily by SALT, that extra tax you pay may be permanently unrecoverable.

The ISO Exerciser’s Trap: When Credits Get Stuck

Even though the ISO bargain element generates a recoverable AMT credit, there’s a practical trap: you can only use the credit in years when your regular tax exceeds your AMT.

If you exercise ISOs year after year, you may find yourself perpetually subject to AMT. Your regular tax is $X, but your AMT is higher, so you pay AMT. Each year, you generate an AMT credit, but you can’t use it because you’re subject to AMT again. The credit accumulates, unused.

When the Credit Becomes Usable: The Stock Sale Year

The credit typically becomes usable when you sell the ISO shares. Here’s why:

In the year you exercise an ISO, you add the bargain element to your AMTI. In the year you sell those shares, you effectively get to subtract the bargain element back out of your AMTI calculation. This reversal substantially lowers your AMTI that year — frequently making it a sizable negative adjustment.

At the same time, selling the shares creates a capital gain. Both the regular tax and AMT systems allow favorable treatment for long-term capital gains, so the gain itself is taxed at long-term capital gains rates under both systems. But because the bargain element is now subtracted from AMTI under the AMT system (and not under regular tax), your AMT liability ends up lower than your regular tax.

This creates a year where regular tax exceeds AMT, allowing you to claim accumulated AMT credit — to the extent of that excess. Frequently, the bargain element subtraction is so large that it allows you to recover all or most of your accumulated credit in the sale year. But this isn’t guaranteed: depending on the size of your accumulated credit and the size of the excess, you may recover all of it, some of it, or only a portion. Any unused credit continues to carry forward.

It’s also worth noting that selling the shares isn’t the only path to recovering the credit — any year where your regular tax exceeds your AMT creates an opportunity to claim some of the credit. But for ISO exercisers who remain in AMT territory year after year, the sale year is typically when the bulk of the recovery happens.

The Takeaway

The AMT can affect high-income earners in many ways, though two of the most common triggers are exercising ISOs and claiming large SALT deductions. Understanding which one applies to you matters because the tax consequences are different. If your AMT is driven by ISO exercises, you may be able to recover that AMT in future years — potentially substantially when you sell the shares, as the bargain element reverses and creates a year where regular tax exceeds AMT. If your AMT is driven by SALT, that AMT is permanently lost with no recovery mechanism. For those exercising ISOs or living in high-tax states, understanding your AMT exposure and recovery potential is important for long-term planning.