What this line means
Your recalculated income tax based on the corrected taxable income on line 5. Column A is the tax from your original return (line 16 of Form 1040). Column B is the change in tax. Column C is the corrected tax. Use the Tax Table or Tax Computation Worksheet for the year you are amending — not the current year’s rates.
Does this apply to you?
- You changed taxable income on line 5 and need to recalculate the tax
- You used the wrong tax table or worksheet on your original return
- You failed to use the Qualified Dividends and Capital Gain Tax Worksheet when you had qualifying income
- You need to correct an error in the tax computation itself
Easy to overlook
Use the tax rates from the year being amended Tax brackets change annually. If you are amending a 2023 return in 2026, use the 2023 Tax Table — not the 2025 or 2026 rates. The Form 1040-X instructions specify which year’s rates to use. Filing with the wrong year’s rates changes the tax amount and triggers a correction from the IRS. 1 IRS Form 1040-X Instructions — Line 6
Recalculate qualified dividends and capital gains tax If your amendment changes the amount of qualified dividends or long-term capital gains, you must redo the Qualified Dividends and Capital Gain Tax Worksheet to get the correct tax on line 6. Using the standard Tax Table for income that qualifies for lower capital gains rates overstates your tax. 2 General filing pattern — using wrong year’s tax table
Watch out for this
Entering the tax change in Column B as the absolute difference without the correct sign. If your corrected tax is lower than the original (you are amending to reduce tax), Column B is a negative number. If the corrected tax is higher (you are reporting additional income), Column B is positive. The sign on Column B drives whether you get a refund or owe more.
Footnotes
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IRS Form 1040-X Instructions, Line 6. https://www.irs.gov/instructions/i1040x ↩
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IRS Form 1040-X Instructions, Tax Computation. https://www.irs.gov/instructions/i1040x ↩