What is Form 6251?
Form 6251 calculates the Alternative Minimum Tax (AMT). It starts with AGI, adds back state and local tax (SALT) deductions, private activity bond interest, and other preference items to arrive at Alternative Minimum Taxable Income (AMTI). After subtracting the AMT exemption, the result is taxed at 26% (first $232,600 in 2025) or 28%. AMT is owed only if the tentative minimum tax exceeds regular tax.
SupportedKey Lines
| Line | Description | Destination |
|---|---|---|
| Line 1 | Taxable income (from Form 1040) | Starting point |
| Line 2a | SALT addback | Major AMT preference |
| Line 7 | Alternative Minimum Taxable Income (AMTI) | Before exemption |
| Line 9 | AMT exemption | Filing-status based |
| Line 11 | Tentative minimum tax minus regular tax | Schedule 2 Line 1 |
How PaisaTax Handles It
- Fully computed from Form 1040 taxable income plus preference addbacks
- SALT addback is the primary trigger for most taxpayers (Schedule A state/local taxes)
- AMT exemption phases out at high income levels
- AMT due only when tentative minimum tax exceeds regular tax liability
Common Situations
- High SALT deduction: Taxpayer deducts $10,000 SALT on Schedule A — added back for AMT, potentially triggering additional tax.
- No AMT due: Most filers find their regular tax exceeds tentative minimum tax, resulting in zero AMT.
- AMT exemption phase-out: Very high income reduces the exemption, increasing AMTI subject to AMT rates.