The Quiet Tax That Could Erase Your Refund: Understanding AMT Exposure Before 2026 Arrives

A Tax System Running in the Background

Most taxpayers are familiar with the standard income tax calculation — apply deductions, claim credits, arrive at a liability. What far fewer people appreciate is that the IRS runs a second, parallel calculation alongside that one. The Alternative Minimum Tax, commonly referred to as the AMT, was originally enacted in 1969 to ensure that wealthy individuals could not eliminate their tax liability entirely through aggressive deductions. Decades later, it has evolved into a trap that ensnares professionals, business owners, and even upper-middle-income households who would never consider themselves tax shelter architects.

The mechanics are straightforward in concept but punishing in practice. You calculate your regular tax liability, then recalculate your income under the AMT framework — adding back certain deductions and preference items — and pay whichever figure is higher. If the AMT calculation produces a larger number, the difference becomes an additional tax owed. Refunds shrink. In some cases, they vanish entirely.

With the Tax Cuts and Jobs Act (TCJA) provisions scheduled to sunset after 2025, AMT exemption thresholds are set to revert to significantly lower levels beginning in 2026. That creates a narrow window in which planning can meaningfully reduce your exposure.

What Triggers AMT Liability

Not every taxpayer faces AMT risk, but certain financial profiles carry substantially elevated exposure. Understanding which factors feed the AMT calculation is the first step toward managing it.

Incentive Stock Options (ISOs): This is one of the most common and most surprising AMT triggers for employees at technology companies and startups. When you exercise an ISO, the spread between the exercise price and the fair market value of the stock is not recognized as ordinary income for regular tax purposes. Under the AMT, however, that spread is treated as an adjustment and added to your alternative minimum taxable income (AMTI). In a year when you exercise a large block of options — particularly if the underlying stock has appreciated significantly — this single event can push your AMT liability into five or six figures.

State and Local Tax Deductions: Under regular tax rules, taxpayers who itemize can deduct state and local taxes up to the $10,000 cap established by the TCJA. Under the AMT framework, this deduction is disallowed entirely. For residents of high-tax states such as California, New York, New Jersey, or Illinois, this addback alone can substantially increase AMTI.

Passive Activity Losses: Certain passive losses from real estate investments or limited partnership interests that reduce your regular taxable income are disallowed under the AMT calculation, increasing your AMTI.

Accelerated Depreciation: Business owners who take advantage of bonus depreciation or Section 179 deductions to reduce taxable income in the current year may find that a portion of those deductions are subject to AMT adjustment, depending on the asset type and the depreciation method used.

Large Miscellaneous Deductions: Though the TCJA eliminated most miscellaneous itemized deductions through 2025, taxpayers should be aware that a broader set of deductions becomes unavailable under AMT rules, and the return of pre-TCJA rules in 2026 will expand this exposure further.

The 2026 Exemption Cliff: Why the Timeline Matters

The TCJA dramatically increased AMT exemption amounts and raised the income thresholds at which those exemptions begin to phase out. For 2025, the exemption for single filers stands at approximately $88,100, and for married filing jointly, approximately $137,000. These figures are indexed for inflation and represent a substantial buffer that shields many taxpayers from AMT liability.

If Congress does not act to extend or make permanent the TCJA provisions, those exemptions revert in 2026 to pre-TCJA levels — roughly $55,400 for single filers and $86,200 for married couples. The phase-out thresholds also fall sharply. The practical consequence is that a considerably larger population of taxpayers will find themselves subject to AMT beginning with their 2026 returns, filed in 2027.

For households earning between $200,000 and $750,000 — a range that sits squarely in the AMT crosshairs — the shift could be jarring. Proactive modeling now, while TCJA exemptions remain in place, is not merely prudent. It is arguably essential.

Modeling Your Exposure Before Year-End

The most effective defense against an unexpected AMT bill is a thorough projection of your AMTI before December 31. This involves running a parallel tax calculation that adds back your ISO spreads, disallows your state tax deductions, and adjusts for any depreciation preferences. Tax software can perform this calculation, but working with a qualified tax advisor to interpret the results and test alternative scenarios is considerably more valuable than a static number.

Several questions should guide that conversation:

• What is your current AMTI projection for 2025, and how does it compare to your AMT exemption?
• Do you have unexercised ISOs with significant built-in appreciation? Is it more advantageous to exercise some or all of them in 2025, while exemptions remain elevated, rather than waiting?
• Can you defer income into 2025 to absorb AMT-preferred treatment, or does acceleration into 2025 worsen your position?
• Are any passive losses scheduled to be recognized this year that might interact unfavorably with your AMTI?

The answers will differ substantially depending on your income composition, filing status, and the specific assets and entities involved in your financial picture.

Restructuring Strategies Worth Considering

Once you understand your exposure, several strategies may help reduce or eliminate AMT liability.

Timing ISO Exercises Carefully: If you hold incentive stock options, the decision of when to exercise — and how many shares to exercise in a single tax year — directly controls your AMT exposure. Spreading exercises across multiple years, or limiting exercises to an amount that keeps your AMTI below the exemption threshold, can prevent a single-year spike.

Converting to Nonqualified Stock Options (NSOs) in Certain Circumstances: Unlike ISOs, NSOs generate ordinary income upon exercise, which is subject to regular income tax but does not create an AMT preference item. In some cases, this trade-off is favorable depending on your overall tax rate environment.

Accelerating Deductions That Are AMT-Neutral: Charitable contributions, for example, are deductible under both the regular tax system and the AMT. Concentrating charitable giving in years where you face elevated AMT exposure allows you to reduce both regular and alternative minimum taxable income simultaneously.

Harvesting Capital Gains Strategically: Long-term capital gains are taxed at preferential rates under both the regular tax and the AMT. In some scenarios, recognizing gains rather than deferring them can be structured to absorb available AMT credits from prior years, effectively converting a previously paid AMT liability into a current-year offset.

Utilizing Prior-Year AMT Credits: If you paid AMT in a previous year — particularly due to ISO exercises — you may have accumulated a Minimum Tax Credit (MTC) that can be applied against your regular tax liability in subsequent years when your regular tax exceeds your tentative minimum tax. Tracking and deploying this credit appropriately is an often-overlooked opportunity.

The Cost of Waiting

The AMT does not announce itself in advance. It surfaces when you file your return — sometimes months after the decisions that triggered it have already been made and cannot be undone. Stock options exercised in January are history by December. Depreciation taken in the first quarter is already claimed. Income recognized in the spring is already taxable.

The strategies available to manage AMT exposure are, almost without exception, decisions that must be made before year-end. A projection completed in October or November leaves meaningful room to act. A projection completed in February leaves almost none.

For high-income earners and business owners navigating a complex deduction landscape, the AMT represents one of the more consequential — and underappreciated — risks in the current tax environment. The impending sunset of TCJA exemption levels makes that risk considerably more acute. Addressing it now, while the planning window remains open, is precisely the kind of forward-looking strategy that separates an optimized tax position from an expensive surprise.