Alternative Minimum Tax

The Alternative Minimum Tax (AMT) is a parallel calculation that runs alongside the standard income tax, imposing a floor on the effective tax rate paid by high earners. By disallowing or limiting certain deductions and credits that would otherwise let the wealthy reduce their tax bill to near-zero, it prevents sophisticated tax planning from gutting the progressive tax system—though its design has created a costly, unpopular compliance burden with limited revenue gains.

The problem it solves

The standard income tax allows deductions for many outlays: mortgage interest, charitable donations, state and local taxes, business losses. These are intended to match taxable income to true economic capacity—you shouldn’t be taxed on income immediately lost to a deductible expense. But in combination, they can be abused. A wealthy person with a passive investment loss, high deductible state taxes, and large charitable contributions might pay tax on very little income despite earning millions, while middle-class workers—with fewer deductions—face higher effective rates.

This perverse outcome offended policymakers’ sense of fairness. In the 1960s, politicians discovered that a handful of very-high-income Americans were paying almost no federal income tax because cascading deductions, credits, and exclusions had eroded their tax base. The public outcry led to the AMT, introduced in 1969 as a backstop: if your calculated tax is unusually low, you recalculate under tougher rules and pay whichever is higher.

How it works

The AMT calculation starts from income but adds back or disallows certain items that reduce taxes under the standard system:

• Deductions eliminated or capped: State and local taxes (SALT), mortgage interest on second homes, and miscellaneous business expenses are partially or fully disallowed.
• Exclusions lost: Tax-exempt-bond interest is included; deductions for medical expenses tighten.
• Credits limited: Most tax credits are unavailable or restricted.

After these adjustments, you apply the AMT rate (26% or 28%, depending on bracket) to the “alternative minimum taxable income” (AMTI). If this exceeds your regular tax, you pay the AMT instead.

The AMT exemption—a floor below which you don’t calculate AMT—was originally high, shielding typical earners. But because the exemption wasn’t indexed to inflation, it gradually caught more and more middle-income taxpayers over decades. By the 2000s, millions of ordinary workers with no sophisticated tax planning were forced to calculate AMT, creating huge compliance costs.

Congress periodically raised the exemption to prevent this “bracket creep,” but without a permanent inflation adjustment, the problem returned annually. The 2017 tax overhaul significantly raised the exemption, shrinking the AMT population, but the underlying design flaw remains.

Design flaws and unintended consequences

The AMT was meant to target the wealthy using aggressive shelters. Instead, it became a compliance nightmare for ordinary professionals—doctors, lawyers, engineers in high-tax states—who earned substantial income (over $200k), took normal deductions (mortgage, SALT, charitable giving), and were automatically in AMT calculation range. They hired accountants to navigate the parallel system, increasing costs without raising revenue (many AMT bills are small).

A second problem: the AMT was not inflation-indexed (until temporarily adjusted in 2001). This meant each year’s nominal income growth pushed more earners into AMT, even if real income was stable. By the 1990s, the AMT was collecting roughly 1% of federal income-tax revenue but imposing compliance costs far exceeding that. Economists across the political spectrum called for reform.

The 2017 Tax Cuts and Jobs Act nearly doubled the AMT exemption to $109,400 (for single filers), reducing the population subject to AMT dramatically. However, it declined without action, and Congress must periodically extend it or let more taxpayers fall into the calculation.

Why it hasn’t solved the problem

High-net-worth individuals who use aggressive tax shelters—partnerships, options strategies, timing of losses and gains—are often still strategic enough to minimize their standard tax below their AMT. But the AMT also catches ordinary earners with no shelter, making it a blunt and unfair tool.

Moreover, the AMT applies to income and deductions, but modern shelters often work through entities (S-corps, partnerships, pass-through entities) that limit the individual’s reported income in the first place. The AMT calculates from income that’s already been minimized, so it doesn’t recapture much. A founder of a pass-through business that generates $10 million of economic gain but is structured to report $1 million in taxable income may owe AMT on the $1 million, not the $10 million.

Comparison to other anti-avoidance tools

Most democracies address tax avoidance through different mechanisms. Some use a “general anti-avoidance rule” (GAAR)—a principle that says if a transaction’s main purpose is tax avoidance with no genuine business reason, it’s disallowed. Others use specific rules targeting particular shelters (loss-limitation rules, passive-activity restrictions). The U.S. has bits of both, but the AMT remains the most visible (and resented) catch-all.

The Alternative Minimum Tax is in some ways a crude predecessor to more modern anti-avoidance tools. A well-designed GAAR—combined with country-by-country reporting and international tax cooperation—might be more effective and less costly to comply with.

Why it persists

Despite its flaws, the AMT survives because it represents a political commitment to a principle: high earners should pay at least some effective tax rate. Eliminating it entirely would signal that deductions and credits can reduce anyone’s tax to near-zero without consequence. Policymakers resist that message, so they keep the AMT but patch it periodically.

Reform proposals abound. Some advocate repealing it entirely and tightening the standard system instead (disallowing excessive deductions, indexing brackets). Others want to make it simpler and more targeted—say, a surtax on high earners that kicks in if their effective rate is below a threshold. None has cleared Congress, partly because each alternative shifts the tax burden within the high-income group or opens new lobbying battles.

AMT in practice

For most of the 1970s–2010s, the AMT was a real compliance cost for professionals earning over $150k–$250k with modest deductions. Accountants would calculate both systems. A substantial number owed AMT—sometimes thousands of dollars attributable purely to the parallel system’s additional taxes, not genuine additional income.

After the 2017 tax increase in exemptions, the AMT population shrank. But it returned during the pandemic and is expected to creep upward again without adjustment. Individuals inheriting real estate with stepped-up basis and generating passive income are particularly vulnerable.

The AMT also applies to corporations (the “corporate AMT”), though it was weakened in 2017 and effectively repealed in 2018 as the corporate tax rate fell. The individual AMT remains and will reclaim relevance as expiring exemptions phase down.

See also