What this line means
The penalty for underpaying your estimated taxes during the tax year being amended. If your amendment increases your tax liability and you did not have enough withholding or estimated tax payments to cover the corrected amount, the IRS may assess an estimated tax penalty. You calculate this penalty on Form 2210 and enter the result here. The penalty is essentially interest on the underpayment for the period it was underpaid — it is not a flat fee.
Does this apply to you?
- Your amendment significantly increases your tax liability for the year
- You did not have withholding or estimated payments that covered at least 90% of your corrected tax or 100% of your prior year’s tax (110% if AGI exceeded $150,000)
- The IRS sent a notice assessing an estimated tax penalty on your original return, and the amendment changes the calculation
- You want to claim a reduced penalty or a penalty waiver using Form 2210
Easy to overlook
The penalty applies to the corrected tax, not the original When you amend and your tax liability increases, the IRS recalculates whether your estimated payments and withholding met the safe harbor thresholds based on the corrected amount. Payments that were sufficient for the original return can trigger a penalty against the higher corrected tax — unless you met the prior-year safe harbor (100% of your prior year’s tax, or 110% if AGI exceeded $150,000). 1 IRS Form 2210 Instructions — General Instructions
You can request a waiver for unusual circumstances If the underpayment resulted from a casualty, disaster, or other unusual circumstance and imposing the penalty would be against equity and good conscience, you can request a waiver by checking box A on Part II of Form 2210. You can also request a waiver if you retired (after age 62) or became disabled during the tax year or the preceding tax year. 2 IRS Publication 505 — Chapter 4, Underpayment Penalty
Most people should let the IRS calculate it Unless you qualify for a waiver or the annualized income installment method (which can reduce the penalty if your income was uneven throughout the year), the IRS will calculate the penalty for you when they process the amended return. Leaving this line blank is acceptable — the IRS computes it and sends you a bill for the difference. 3 IRS Form 1040-X Instructions — Line 20
The annualized income installment method can save you money If you earned most of your income late in the year (for example, a large capital gain in Q4), the standard penalty calculation overstates what you owe. Schedule AI of Form 2210 lets you prove that your payments matched the tax owed for each quarter. This often eliminates or sharply reduces the penalty. 4 IRS Form 2210 Instructions — Schedule AI
Watch out for this
Assuming you owe a penalty when you might not. The safe harbor rule protects you if your total payments (withholding plus estimated payments) covered at least 100% of your prior year’s tax liability (110% if your AGI exceeded $150,000). Even if your amended return shows a large increase in tax, you may not owe an estimated tax penalty at all if the safe harbor was met based on the prior year. Check before filing Form 2210 — you may save yourself unnecessary paperwork and payment.
Footnotes
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IRS Form 2210 Instructions, General Instructions. https://www.irs.gov/instructions/i2210 ↩
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IRS Publication 505, Chapter 4, Underpayment Penalty. https://www.irs.gov/pub/irs-pdf/p505.pdf ↩
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IRS Form 1040-X Instructions, Line 20. https://www.irs.gov/instructions/i1040x ↩
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IRS Form 2210 Instructions, Schedule AI. https://www.irs.gov/instructions/i2210 ↩