Alternative Minimum Tax (AMT) Explained: Do You Owe It?
In taxes, there’s a kind of equalizer — a parallel system called the alternative minimum tax, or AMT. Instituted in 1969, the AMT was designed to ensure that high-income taxpayers couldn’t use deductions and credits to pay a lower effective tax rate than everyone else.
In past years, the AMT wasn’t limited to the very wealthy. Because it wasn’t indexed for inflation until 2013, millions of middle-class Americans found themselves unexpectedly subject to it. The Tax Cuts and Jobs Act (TCJA) of 2017 significantly narrowed the AMT’s reach, and the One Big Beautiful Bill Act (OBBBA), signed into law in 2025, made those higher exemption amounts permanent — while also introducing some new changes taxpayers should understand.
What Is the AMT, Exactly?
The AMT is best understood as a separate tax system with its own set of rules for deductions — rules that are generally more restrictive than those under the traditional tax system. Taxpayers must calculate their liability under both the regular tax system and the AMT system, and pay whichever amount is higher.
The only way to know for certain whether you owe the AMT is to complete Form 6251 from the Internal Revenue Service. This may be worth doing even if you’re unsure, particularly if you’re a high-income earner who claims sizable tax breaks — since many traditional deductions, such as personal exemptions and certain state and local tax deductions, are limited or unavailable under AMT rules.
If you should have paid the AMT and the IRS later discovers that you didn’t, you may owe back taxes, plus interest and potential penalties.
How Does the AMT Work? Current Exemption Amounts
Under OBBBA, the AMT exemption amounts established by the TCJA were made permanent and continue to be adjusted annually for inflation. For the 2026 tax year:
- Single filers: Exemption of $90,100, with phase-out beginning at $500,000 of alternative minimum taxable income (AMTI).
- Married filing jointly: Exemption of $140,200, with phase-out beginning at $1,000,000 of AMTI.
What Changed Under OBBBA
While the higher exemption amounts are now permanent, OBBBA also introduced a less favorable change starting in 2026:
- Phase-out thresholds are lower than they were under the TCJA’s 2025 rules — dropping from $626,350 (single) and $1,252,700 (married filing jointly) to the reduced 2026 levels above.
- The phase-out rate doubled, from 25% to 50%. This means the AMT exemption is lost more quickly as income rises above the threshold.
As a result, some higher-income taxpayers who weren’t previously subject to the AMT may find themselves partially or fully exposed to it starting in 2026, even though the base exemption amount itself increased.
Why Understanding the AMT Matters
Because AMT rules involve complicated provisions, it’s a good idea to consult a legal or tax professional for guidance specific to your situation. If you want to avoid surprises at tax time, understanding where you stand on the AMT is worth the time and effort — especially given the phase-out changes now in effect.
Frequently Asked Questions
What is the AMT tax?
The alternative minimum tax (AMT) is a separate tax system, established in 1969, designed to ensure high-income taxpayers pay a minimum level of tax even if they qualify for significant deductions or credits under the regular tax system. Taxpayers calculate their liability under both systems and pay whichever is higher.
How does the AMT work?
The AMT works by requiring certain taxpayers to add back specific deductions and tax preference items to their income, then subtract an AMT exemption based on filing status, and apply the AMT tax rate. If this AMT liability exceeds what’s owed under the regular tax system, the taxpayer pays the higher amount.
What are the current AMT exemption amounts?
For the 2026 tax year, the AMT exemption is $90,100 for single filers and $140,200 for married couples filing jointly. These amounts are adjusted annually for inflation under provisions made permanent by the One Big Beautiful Bill Act.
How do I know if I owe the AMT?
The only definitive way to know if you owe the AMT is to complete IRS Form 6251. This is especially worth doing if you’re a high-income earner claiming significant deductions, since many traditional tax breaks are limited under AMT rules.
Did the AMT rules change recently?
Yes. The One Big Beautiful Bill Act (OBBBA), signed in 2025, made the TCJA’s higher AMT exemption amounts permanent but lowered the phase-out thresholds and doubled the phase-out rate from 25% to 50%, starting in 2026 — meaning some higher earners may face greater AMT exposure than in recent years.
For individuals and families in Fort Myers and across Southwest Florida navigating these AMT changes, working with a fee-only fiduciary financial planning team can help you understand your exposure and plan accordingly.
This material is not intended as tax or legal advice and may not be used for the purpose of avoiding federal tax penalties. Please consult a qualified legal or tax professional regarding your specific situation.
