Alternative Minimum Tax (2026)

When regular tax is not the final word

The alternative minimum tax parallel system recalculates tax with add-backs and adjustments—state taxes, certain deductions, ISO spread at exercise, and other preferences. You owe AMT when tentative minimum tax exceeds regular income tax. Middle-income filers rarely hit AMT today, but equity compensation and high SALT states still create landmines.

Enter regular taxable income, preference items, and filing status. The calculator applies 2026 exemption amounts (~$90,100 single, ~$140,200 married filing jointly), phaseout rules, and 26%/28% AMT rates to estimate incremental AMT.

2026 AMT building blocks

• Exemption: ~$90,100 single / ~$140,200 MFJ (IRS 2026 inflation)
• Phaseout begins at higher AMTI thresholds—exemption shrinks 25 cents per dollar above phaseout range
• Rates: 26% on AMTI up to statutory breakpoint, 28% above
• Compare tentative minimum tax to regular tax; pay excess as AMT

Exact phaseout thresholds follow Rev. Proc. 2025-32 and IRS newsroom 2026 inflation releases—enter adjustments if your preparer supplies precise Form 6251 inputs.

ISO exercises and AMT

Incentive stock option spread at exercise is often not regular income but is an AMT adjustment. Exercising and holding ISOs can produce large AMT bills without cash from selling shares—classic planning problem. Model exercise in the stock options calculator, then feed AMT preferences here.

How to use the calculator

Step 1 — Start from regular tax

Enter regular income tax after credits from the federal income tax calculator or your records.

Step 2 — Add AMT preferences

State and local tax deduction add-back, ISO spread, private activity bond interest, and other Form 6251 lines you know apply.

Step 3 — Read incremental AMT

Output shows tentative minimum tax minus regular tax when positive—your AMT cash cost for planning.

Worked example sketch

Married filing jointly, regular tax $45,000, AMTI after preferences $320,000. Exemption ~$140,200 phases down at high AMTI. Tentative minimum tax might exceed regular tax by $8,000–$15,000 depending on exact preferences—run your numbers above rather than relying on rules of thumb.

SALT and deductions

Regular tax limits state and local tax deductions; AMT adds back unreimbursed employee expenses and taxes in the preference stack. Itemizers in high-tax states should not assume SALT cap alone eliminates AMT risk when ISOs or other preferences exist. Compare itemized path with the standard vs itemized calculator.

AMT credit planning

AMT paid on deferral items can generate minimum tax credit in later years. Multi-year modeling is beyond this single-year tool—track Form 8801 carryforward with your preparer when ISO exercises trigger AMT.

Common mistakes

• Ignoring AMT when exercising ISOs because regular tax did not change
• Assuming AMT only affects millionaires
• Double-counting preferences already in taxable income
• Forgetting exemption phaseout at high AMTI

Related tools

ISO exercises: stock options calculator. QSBS exclusions interact with AMT in complex ways—see QSBS calculator with manual eligibility. Federal baseline: federal income tax calculator.

Preference items beyond ISO and SALT

Private activity bond interest, depletion preferences, and certain depreciation adjustments on leased equipment can stack with ISO spread and state tax add-back. Real estate investors using accelerated depreciation on rental property may see AMT adjustments even when rental losses are passive-limited separately on Form 8582.

Exercise caution when large itemized deductions interact with AMT: medical expenses above 7.5% AGI help regular tax but other deductions may not help AMT when preferences dominate.

Planning levers before year-end

Spreading ISO exercises, paying fourth-quarter state estimated taxes before December 31 (affects timing but not always AMT add-back), and timing capital gain recognition can shift AMTI across years. Charitable contributions reduce regular tax but may not reduce AMT when you are preference-driven—verify with full Form 6251 projection.

Form 6251 line-by-line mindset

Start from taxable income, add AMT preferences (SALT, ISO spread, private activity bond interest), subtract AMT exemption (phased), apply 26%/28% rates, compare to regular tax. Exemption phaseout adds 25 cents of lost exemption per dollar of AMTI above threshold—effective marginal rate can exceed 28% in phaseout band.

State tax refunds in following year may reduce regular tax but AMT add-back in prior year already hurt—multi-year modeling catches refund-taxable-in-next-year interaction under TCJA SALT cap environment.

Children subject to kiddie tax rarely hit AMT alone; parents exercising ISOs with adult children in household still file separate AMT analysis per taxpayer.

Reading your results for amt

The interactive panel above shows a transparent calculation trace in cents—use it to sanity-check inputs before you rely on any number for decisions. Tax software at filing time may differ when every credit, limitation, and state conformity rule is applied in full. Treat output here as structured planning math aligned to 2026 federal reference data where noted, not as e-file output or professional advice.

When your situation includes items this specialized tool simplifies—multiple entities, prior-year carryforwards, treaty elections, or state nonconformity—layer those facts manually or with a preparer. The goal is to narrow uncertainty enough to ask better questions, not to eliminate the need for review when dollars are material.

Recordkeeping that survives scrutiny

Keep source documents (forms, statements, logs, confirmations) that support every input you typed. IRS and state audits often start from third-party reporting; your job is to reconcile 1099s, K-1s, and broker exports to the story you file. Digital backups with dates beat reconstructed spreadsheets created after an notice arrives.

For amt, retain worksheets year to year when carryforwards exist—loss carryovers, credit carryforwards, passive loss suspensions, and basis schedules die silently if you change preparers and lose history.

Related tools on this site

ISO exercises: stock options calculator. QSBS: QSBS calculator. Federal baseline: federal income tax calculator.

2026 federal brackets and payroll context

Ordinary income tax brackets and standard deductions for 2026 follow IRS Rev. Proc. 2025-32 ($16,100 single / $32,200 joint standard deduction; seven marginal rates from 10% to 37%). Social Security tax applies at 6.2% on wages up to the $184,500 wage base; Medicare continues at 1.45% with Additional Medicare Tax above threshold wages. These layers stack independently from specialized rules modeled in this amt tool—run the federal income tax calculator when you need the full return picture.

Quarterly estimated tax may be required when withholding does not cover liability—see the quarterly estimated tax calculator. Year-end refund or balance due comparisons belong in the tax refund estimator once withholding and payments are known.

Sources and methodology

2026 exemption and rate structure from IRS Rev. Proc. 2025-32 and IRS newsroom 2026 inflation adjustments. Form 6251 has additional detail this educational tool simplifies. Not a substitute for tax software or professional advice.