Understanding the IRS Alternative Minimum Tax (AMT) in 2026

What AMT Is — The Parallel Tax System

The Alternative Minimum Tax was created to ensure that high-income taxpayers could not use deductions, credits, and preferences to reduce their regular income tax to zero or near-zero.

The AMT operates as a parallel calculation: (1) calculate regular tax in the ordinary way; (2) calculate AMT separately — starting from a broader income base that adds back certain "preference items"; (3) pay whichever is higher. AMT only applies when the AMT calculation produces a result higher than regular tax (IRC §55).

The AMT Formula

Step 1: Start with regular taxable income (from Form 1040)
Step 2: Add back AMT preference items and adjustments:
  + State and local tax deductions (SALT) previously deducted
  + ISO bargain element (FMV minus exercise price at exercise)
  + Accelerated depreciation in excess of straight-line
  + Certain passive activity deductions
  = Alternative Minimum Taxable Income (AMTI)

Step 3: Subtract the AMT exemption
  Single: $89,500 (2026)
  MFJ: $139,400 (2026)
  = AMTI after exemption

Step 4: Apply AMT rates
  26% on AMTI up to $232,600
  28% on AMTI above $232,600
  = Tentative Minimum Tax (TMT)

Step 5: Compare
  If TMT > regular tax → pay TMT (you have an AMT bill)
  If regular tax ≥ TMT → no AMT due

Source: IRC §55; Form 6251 instructions.

Common AMT Triggers Post-TCJA

TCJA dramatically curtailed the AMT's reach by raising the exemption substantially and increasing phase-out thresholds. For most filers, SALT and miscellaneous itemized deductions are no longer meaningful AMT triggers.

1. Incentive Stock Option (ISO) exercises:This is the dominant AMT trigger for working professionals today. When you exercise an ISO, you don't pay regular income tax at exercise. However, the "bargain element" — the difference between the fair market value (FMV) and your exercise price — is treated as an AMT preference item and added to AMTI. A large bargain element can create a massive AMT bill even for someone with modest regular income.

2. Accelerated depreciation: Businesses and landlords who use accelerated depreciation methods (MACRS, bonus depreciation) must use a slower schedule for AMT purposes, creating an add-back.

3. Certain tax-exempt income: Some private activity bond interest that is tax-exempt for regular purposes is an AMT preference item.

2026 AMT Exemption and Phase-Out Thresholds

Per Rev. Proc. 2025-32 §3.20:

Phase-out mechanics: For every dollar of AMTI above the phase-out start, the exemption is reduced by $0.25. A single filer with AMTI of $726,350 (exactly $100,000 above $626,350) sees the exemption reduced by $25,000: $89,500 − ($100,000 × 25%) = $64,500.

Worked Example — California ISO Holder

Profile: Single filer. W-2 wages: $200,000. Exercised 10,000 ISO shares at $10 strike price when FMV was $100. Bargain element: ($100 − $10) × 10,000 = $900,000.

Regular tax calculation:
W-2 wages: $200,000
Standard deduction: $16,100
Taxable income: $183,900
Federal income tax (regular): ~$36,984

AMT calculation:
Regular taxable income: $183,900
Add: ISO bargain element: $900,000
AMTI: $1,083,900

AMT exemption (single): $89,500
Phase-out: AMTI $1,083,900 exceeds $626,350 by $457,550
Exemption reduction: $457,550 × 25% = $114,388 → exceeds $89,500 → exemption = $0
AMTI after exemption: $1,083,900

AMT tax:
26% on $232,600 = $60,476
28% on ($1,083,900 − $232,600) = 28% × $851,300 = $238,364
Total Tentative Minimum Tax (TMT): $298,840

AMT excess: $298,840 − $36,984 = $261,856

Result: $261,856 additional AMT on top of regular tax. Total federal income tax: approximately $298,840.

Strategies — Managing ISO Exercise AMT

1. Exercise in low-AMT years. Spread ISO exercises across multiple years. Model the AMT breakeven before exercising — exercise enough shares that the bargain element stays below the AMT exposure zone.

2. Early exercise (83(b) election). For early-stage startups with low FMV, exercising immediately after grant (when FMV ≈ strike price) minimizes or eliminates the bargain element. This requires filing an 83(b) election within 30 days of exercise.

3. Track the AMT credit carryforward. When you pay AMT due to an ISO exercise and later sell the stock (recognizing the gain as regular income), the prior AMT may convert to an AMT credit that offsets future regular tax — see below.

4. Charitable stock donations. If you hold appreciated ISO stock (post-exercise, post-holding-period), donating it to charity avoids the capital gains tax. Complex; consult a tax professional.

The AMT Credit — Recovery in Later Years

When you pay AMT due to "deferral" preference items (like ISO bargain elements), you generate an AMT credit (Form 8801). This credit can offset regular tax in future years when your regular tax exceeds your AMT calculation.

In essence: the AMT collected on the ISO bargain element is not permanently lost. When you eventually sell the ISO stock and pay regular capital gains tax, the AMT credit offsets that regular tax liability. The AMT credit carries forward indefinitely.

Frequently Asked Questions

Estimate Your Full Federal Liability with the 2026 Federal Income Tax Calculator

AMT calculations are mechanical but detail-sensitive. The ISO bargain element, depreciation adjustments, and exemption phase-outs all interact. The 2026 federal income tax calculator includes AMT as part of the full liability estimate for filers with ISO income or other AMT-relevant inputs. The capital gains tax calculator helps model the gain side when ISO shares are eventually sold.