Instructions for Form 6251 — 2018 Tax Year Checklist
Introduction
Form 6251 is used to determine whether an individual owes Alternative Minimum Tax for the
2018 tax year under rules shaped by the Tax Cuts and Jobs Act. The calculation ensures certain tax benefits are limited when the Alternative Minimum Taxable Income exceeds the exemption thresholds.
This checklist explains how to complete Form 6251 using the correct 2018 line references, including Part II Alternative Minimum Tax computations and Line 29 comparisons. It applies to
Form 1040 filers and certain Form 1040NR filers who must compute Alternative Minimum Tax under the Alternative Minimum Tax section.
Why This Form Is Required For 2018
The Alternative Minimum Tax system requires taxpayers to recompute income using adjusted rules that add back preference items and recalculate allowable deductions. If the tentative minimum tax exceeds the regular tax, the difference becomes the Alternative Minimum Tax due for the year.
For 2018, exemption amounts and phaseout thresholds changed under the Tax Cuts and Jobs
Act, affecting how many filers must complete Form 6251. Certain credits, including the foreign tax credit, may also require limitation calculations under the Alternative Minimum Tax.
What Happens If Form 6251 Is Ignored
If the Alternative Minimum Tax applies and Form 6251 is not completed, the return may understate total tax liability. This can result in additional assessments, interest, and potential penalties once the Internal Revenue Service reviews the return.
Failure to calculate the Alternative Minimum Tax correctly may also affect carryforwards and future credit limitations. Errors in the alternative minimum tax section can distort basis tracking, especially when incentive stock options or depreciation adjustments are involved.
Step-by-Step Checklist (2018)
Step 1: Confirm whether Form 6251 is required
Review the 2018 Form 1040 and determine whether preference items, incentive stock options, or credit limitations require Alternative Minimum Tax computation. Compare the tentative minimum tax to the regular tax using the 2018 instructions before deciding whether to file.
Step 2: Establish the correct starting point on Line 1
Begin with regular taxable income from the 2018 Form 1040, adjusting as instructed when taxable income is zero. Follow the Exemption Worksheet carefully because exemption amounts and phaseouts differ from regular tax rules.
Step 3: Adjust state and local taxes properly
Enter adjustments for state and local tax deductions on the appropriate line according to the
2018 Form 6251 instructions. Do not rely solely on regular tax limits, because the Alternative
Minimum Tax disallows certain deductions entirely.
Step 4: Include private activity bond interest
Report specified private activity bond interest as required for Alternative Minimum Tax purposes using Form 1099-INT records. Reduce the amount by related allowable deductions, but never below zero under the 2018 rules.
Step 5: Recompute passive and at-risk limitations
Refigure passive activity losses and at-risk limitations using Alternative Minimum Tax methods rather than regular tax worksheets. Enter the resulting adjustment difference on the applicable
Form 6251 line.
Step 6: Recalculate depreciation differences
Depreciation for assets placed in service after 1986 must be recomputed using Alternative
Minimum Tax methods. Publication guidance should be consulted to ensure that the correct depreciation adjustments are reflected.
Step 7: Report incentive stock option adjustments
If incentive stock options were exercised and shares were not sold in the same year, compute the adjustment based on fair market value and exercise price. Maintain accurate basis records because later dispositions affect both regular tax and Alternative Minimum Tax reporting.
Step 8: Review optional deduction elections
Confirm whether certain elections allow identical treatment under regular tax and Alternative
Minimum Tax rules. Only exclude adjustments when the 2018 instructions explicitly permit similar computation.
Step 9: Apply net operating loss limitations correctly
Compute any Alternative Tax Net Operating Loss Deduction according to the 2018 framework.
Review the loss origin years carefully because different limitation rules may apply.
- Full IRS transcript retrieval (Wage & Income + Account)
- Professional tax form review
- Preparation & filing support
- Tax relief options if you owe the IRS
Step 10: Compute the tentative minimum tax and compare
Complete Part II, Alternative Minimum Tax, and determine the tentative minimum tax amount.
Compare it to regular tax and report any difference on Line 29 of the 2018 Form 1040 as required.
What Happens After The Calculation Is Completed
If Alternative Minimum Tax applies, transfer the computed amount to the correct line of the 2018 return and attach Form 6251. Confirm that related credits, including the foreign tax credit, reflect proper limitation under Alternative Minimum Tax rules.
Maintain detailed records to support depreciation schedules, private-activity bond interest, and incentive stock option basis calculations. Accurate documentation protects future reporting and clarifies adjustments during any later review or Q&A interview with the Internal Revenue
Service.
Common Mistakes To Avoid
One standard error is using line references from a different tax year, which can distort the
Alternative Minimum Tax calculation. Another frequent mistake is failing to adjust for disallowed deductions when computing Alternative Minimum Taxable Income.
Some filers overlook interactions between earned income, self-employment tax adjustments, and Alternative Minimum Tax limitations. Others neglect to update exemption amounts based on filing status and January 1 birthdays that affect age-related eligibility.
Frequently Asked Questions
Is Form 6251 required for every taxpayer?
No, Form 6251 is required only when Alternative Minimum Tax rules apply or when certain credits trigger limitation calculations. Many taxpayers will not owe Alternative Minimum Tax for
2018 due to increased exemption amounts.
Does the Alternative Minimum Tax apply to Form 1040NR filers?
Certain Form 1040NR filers may be subject to an alternative minimum tax depending on their income type and adjustments. The instructions for Forms 6251 and 1040NR provide specific guidance.
Can tax software calculate the Alternative Minimum Tax automatically?
Most commercial software, including TaxAct, includes automated Alternative Minimum Tax computations. However, taxpayers remain responsible for entering complete and accurate information.
How does the foreign tax credit interact with the Alternative Minimum Tax?
The foreign tax credit may be limited under Alternative Minimum Tax rules, requiring a separate calculation. Form 6251 instructions explain how to adjust the credit in the alternative minimum tax section.
Closing
Form 6251 ensures that taxpayers receiving significant tax benefits compute liability under the
Alternative Minimum Tax framework established for 2018. Careful review of Part II, Alternative
Minimum Tax, and Line 29 prevents underreporting and protects future credit calculations.
Maintaining accurate records, including the Exemption Worksheet and basis schedules, supports compliance and reduces future errors. When calculations involve complex items such as incentive stock options or self-employment tax adjustments, professional guidance may be appropriate.
If you’re missing tax documents or want to ensure the numbers you enter match IRS records, we can help.
