Instructions for Form 6251- 2020 Tax Year Checklist
Form 6251 determines whether the Alternative Minimum Tax applies for the 2020 tax year by
comparing a tentative minimum tax to a regular tax after recalculating selected tax benefits under separate federal tax rules. The Alternative Minimum Tax primarily affects noncorporate taxpayers through specific adjustments, such as incentive stock options, depreciation differences, and other preference items defined in the Internal Revenue Code.
This checklist provides a structured, step-by-step reference for completing IRS Form 6251 correctly for 2020, using the proper line sequence, exemption amounts, tax brackets, and comparison methodology tied to Form 1040.
Before The Checklist: Key Preparation Notes
Complete Form 1040 or Form 1040-SR for 2020 as fully as possible before starting Form 6251, because taxable income and regular tax figures flow directly into the AMT computation. Tax preparation software can assist, but all inputs must still follow the 2020 Form 6251 instructions issued by the Internal Revenue Service.
Do not base AMT assumptions on adjusted gross income alone, because the exemption phaseout applies to alternative minimum taxable income rather than AGI. Keep California AMT concepts, Schedule S, and state conformity rules separate from federal AMT calculations.
Ten-Step Checklist
Step 1: Confirm the filing requirement
Confirm whether an AMT computation is required for the 2020 tax year due to incentive stock options, depreciation differences, or other adjustments affecting regular tax benefits. A return may still need Form 6251 when credits or preference items trigger an AMT comparison.
Use the correct 2020 Form 1040 or Form 1040-SR package so Form 6251 line references, AMT exemption amounts, and exemption phaseout thresholds match the proper tax year. This prevents mixing later-year rules with 2020 taxable excess computations and avoids incorrect
Alternative Minimum Tax results.
Step 2: Start with taxable income on line 1
Enter the taxable income from line 15 of Form 1040 or Form 1040-SR on line 1 of Form 6251, as the Alternative Minimum Tax is calculated based on taxable income rather than total tax liability. This starting figure anchors the AMTI build and affects all subsequent adjustment lines.
Confirm taxable income is final before transferring amounts, because changes to Schedule D capital gains, Schedule E activity, or other income sources can alter the tax return baseline.
Recheck calculations after updates so AMT adjustments and tentative minimum tax remain consistent with the final return.
Step 3: Identify applicable AMT adjustments and preferences
Review the tax return for AMT-sensitive items such as incentive stock options, private activity bond interest, depreciation differences, or net operating loss computations that affect alternative minimum taxable income. Only items treated differently under AMT rules should flow into Form
6251.
Work line by line and complete only applicable adjustments, because entering non-applicable amounts can distort AMTI and trigger an incorrect phaseout of the exemption. Keep the AMT worksheets with the tax records, since most worksheets are not included in the filing package.
Step 4: Address deductions under AMT rules
Refigure deductions that receive different treatment under AMT rules, including state and local taxes, certain interest expenses, and itemized deductions that are disallowed or limited for the
Alternative Minimum Tax. These differences often arise when Schedule A deductions reduce regular taxable income.
Follow the Form 6251 instructions for each line rather than applying the regular tax system’s logic, because AMT disallowances are separate from standard deduction rules. Confirm each adjustment reflects the correct tax year treatment, since AMT deduction rules change across years and forms.
Step 5: Compute incentive stock option adjustments
If incentive stock options were exercised during 2020 and not sold in the same year, compute the AMT adjustment based on the spread between fair market value and exercise price. This adjustment can increase AMTI even when the regular tax return shows no immediate income.
Maintain separate AMT basis records for stock options, because later sales can produce different capital gains amounts under regular tax and Alternative Minimum Tax rules. Accurate basis tracking supports tax returns, prevents errors in Schedule D reporting, and preserves the accuracy of future-year AMT credits.
Step 6: Apply depreciation and other preference differences
Refigure depreciation when required under AMT rules, including specific accelerated depreciation methods or preference items that create timing differences from regular tax depreciation. These adjustments often affect business income, rental income, or pass-through entity items reported on the return.
Confirm applicability under the Internal Revenue Code and the Form 6251 instructions, because not every asset requires AMT recomputation, and assumptions can overstate taxable excess.
Keep supporting depreciation schedules with tax records, since AMT recalculations may affect future carryovers and basis.
Step 7: Compute alternative minimum taxable income
Add together taxable income and any necessary adjustments and preference items to get the alternative minimum taxable income, which is used to calculate the AMT exemption and its phaseout. An accurate AMTI determines whether AMT applies and the tentative minimum tax.
Ensure AMTI reflects federal AMT rules only, because state taxes, California AMT concepts, and Schedule CA adjustments do not determine federal Alternative Minimum Tax. Separating federal and state calculations reduces confusion, supports consistent treatment of filing status, and improves overall tax return accuracy.
Step 8: Apply the 2020 AMT exemption and phaseout
Apply the correct 2020 AMT exemption amount for the taxpayer’s filing status, then reduce it when alternative minimum taxable income exceeds the exemption phaseout thresholds. This step determines the taxable excess amount used to compute the tentative minimum tax.
Use the Form 6251 worksheet method instead of estimating, because the phaseout of the exemption depends on AMTI rather than adjusted gross income or regular taxable income.
Confirm filing status selections match the Form 1040 return, since married filing separately uses different thresholds.
Step 9: Calculate tentative minimum tax
Calculate tentative minimum tax by applying the 2020 AMT tax rates to taxable excess after the exemption, using the 26 percent and 28 percent bracket structure. This converts AMTI-based taxable excess into the tentative minimum tax amount for comparison.
If capital gains or qualified dividends are present, use the required AMT capital gains computation method to ensure rates apply correctly across different income levels. This prevents misapplication of tax brackets, supports the correct treatment of Schedule D amounts, and improves consistency across the return.
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Step 10: Compare the tentative minimum tax to the regular tax
Subtract the regular tax amount identified by Form 6251 instructions from the tentative minimum tax to determine whether the Alternative Minimum Tax is owed for the 2020 tax year. AMT applies only when the tentative minimum tax exceeds the regular tax.
Report any AMT due on Schedule 2 of Form 1040, then carry it through the return exactly as directed to avoid misreporting total federal taxes. Retain supporting worksheets and records, because AMT calculations can affect later credits and future-year tax planning.
After The Checklist: Reporting And Filing Notes
Report any AMT liability on Schedule 2 of Form 1040 for 2020, ensuring it flows correctly into total federal taxes owed. Form 6251 itself is attached to the return but is not separately signed or dated.
If a minimum tax credit carryforward exists from prior years, evaluate eligibility using Form 8801 and carry results forward as directed. Retain all AMT worksheets and supporting schedules for records, because AMT basis differences can affect future tax returns.
If you’re missing tax documents or want to ensure the numbers you enter match IRS records, we can help.
