AMT Trigger Calculator

Name: AMT Trigger Calculator
Author: Jacob McEwen

Calculate Alternative Minimum Tax exposure from ISO exercises. Find the maximum number of shares you can exercise without triggering AMT in 2026.

By Jacob McEwen·Updated for 2026 tax year·Editorial standards

Tax planning warning threshold visualization — representing the maximum ISO shares before Alternative Minimum Tax exposure — Photo by Behnam Norouzi on Unsplash

Interactive Calculator

All inputs adjust the result in real time. No data leaves your browser.

Tax Year

Other Annual Income (W-2 + Investment)

Number of ISO Shares to Exercise

Strike Price (per share)

Current Fair Market Value (per share)

Filing Status

AMT Triggered

$83,268Significant AMT — reconsider

Bargain element: $350,000 on $5K shares

Max Safe Shares

$651

Before AMT triggers

Max Safe Bargain

$45,570

Tax-free spread

Exercise Cost

$50,000

$5K shares × $10

Total Share Value

$400,000

At $80 FMV

AMT Calculation

Regular Taxable Income$183,900

ISO Bargain Element (preference)+$350,000

AMTI (Alternative Minimum Taxable Income)$533,900

AMT Exemption−$88,100

AMT Taxable Income$445,800

Tentative AMT (26%/28%)$120,042

Regular Federal Tax$36,774

AMT Owed (if AMT > Regular)$83,268

The Background

When you exercise Incentive Stock Options (ISOs), the spread between the fair market value and the strike price is an Alternative Minimum Tax preference item — even though it's not regular taxable income. This bargain element is added to your AMT income (AMTI), and if AMT exceeds regular tax, you owe the difference.

The 2026 AMT exemption is $88,100 single / $137,000 married, with phase-outs beginning at $626,350 / $1,252,700. The phase-out reduces the exemption by 25 cents per dollar of AMTI over the threshold. AMT rates are 26% on the first $239,100 of AMTI and 28% above.

Strategic implication: the maximum safe exercise (no AMT) is the amount where AMT equals your regular tax. Above that, you pay AMT immediately in cash, even though you have illiquid shares. The classic ISO trap: exercise late in the year, hold for qualifying disposition, watch the stock crash in January, owe AMT on phantom income.

AMT paid is tracked as a credit (Form 8801) and can offset regular tax in future years when regular tax exceeds AMT. So AMT isn't lost forever — it's a prepayment. But the cash flow timing is brutal, and many people exercise more than they can afford to pay.

Equity Compensation Tax Guide 2026: RSUs, ISOs, NSOs, ESPP

The 2026 Complete Tax Guide for High Earners ($200K+)

The Mega Backdoor Roth: Move $30K+ to Roth Every Year

Frequently Asked

Why does exercising ISOs trigger the alternative minimum tax?+

The spread between the strike price and the fair market value at exercise is not income for the regular tax, but it is a preference item for the AMT. Exercise enough shares and the AMT — a parallel calculation at 26% and 28% with its own exemption — exceeds your regular tax, and you owe the difference even though you sold nothing and received no cash.

How many ISO shares can I exercise without AMT?+

Enough that the bargain element, added to your other income, keeps alternative minimum taxable income below the point where AMT overtakes regular tax. The room depends on income, filing status and state; it is typically tens of thousands of dollars of spread for a mid-income filer and shrinks as salary rises. The calculator finds the maximum safe shares for your strike and current value.

What changed for the AMT in 2026?+

The One Big Beautiful Bill Act made the higher exemption amounts permanent but, beginning in 2026, lowered the income at which the exemption starts phasing out to $500,000 for single filers and $1,000,000 for joint filers (indexed), and raised the phase-out rate to 50 cents per dollar. High earners exercising ISOs lose exemption faster than in 2025, so the safe exercise amount is smaller.

Can I get AMT paid on ISOs back?+

Usually, over time. AMT paid because of an ISO exercise generates a minimum tax credit that offsets regular tax in later years when regular tax exceeds AMT, most often the year you sell the shares. The credit can take years to recover, and it is lost value if the shares fall below the exercise price before you sell — which is the real risk of a large exercise.

Is it better to exercise ISOs early in the year?+

An early-year exercise leaves the option of selling before December 31 if the stock falls: a same-year sale is a disqualifying disposition that converts the spread to ordinary income and removes the AMT preference. Exercising in December locks the AMT in with no way to unwind it. Spreading exercises across years, each under the safe amount, avoids AMT entirely.