How Do I Redo My Federal Income Tax If I Forgot to Claim Something?

Tax time is stressful for anyone and as the deadline approaches, taxpayers often rush to avoid late fees and penalties. When you rush to meet that deadline, you might forget to claim a credit or deduction that can reduce your tax bill. The Internal Revenue Service allows you to make adjustments to your income taxes by completing Form 1040-X, which is the Amended U.S. Individual Income Tax Return. The IRS requires that you file your amended return within three years from the date that you filed your original income tax return, or two years after the date you paid the tax, whichever date is later.

Check the box that pertains to the tax year that you are amending on Form 1040-X. If the tax year is not listed on the form, write the year in the field provided.

Enter your personal information in the top part of the form. If you are married, you must also provide your spouse’s information.

Check the box pertaining to your filing status. The IRS doesn’t allow you to change your filing status from married filing jointly to married filing separately after the April 15 deadline.

Complete Column A of the “Income and Deductions,” “Tax Liability” and “Payments” sections using the information on your previously filed income tax return.

Locate the row containing the information that you forgot to claim and enter the correct amount in Column C. The Income and Deductions section contains a row for income, standard and itemized deductions, and exemptions. The Tax Liability section contains a row to claim credits. The Payments section contains a row for federal income tax, earned income credit and refundable credits.

Complete any corresponding schedules to support the change. For example, If you are claiming additional income or expenses from a small business, include Schedule C. If you are amending your return to itemize deductions, fill out Schedule A. If you are claiming the earned income credit, complete Schedule EIC.

Subtract the amount in Column C from Column A to determine the net change. Enter this amount in Column B.

Complete Column C of the “Income and Deductions,” “Tax Liability” and “Payments” for the rows that you did not amend. Enter the same amount listed in Column A. Perform the calculations to determine your taxable income, total tax and total payments.

Complete the “Refund or Amount You Owe” section to determine the amount of your overpayment.

Complete “Part I” if you are claiming additional exemptions on the amended return. You must also list the name, Social Security number and relationship of each exemption in this section.

Check the box pertaining to whether you would like to contribute to the Presidential Election Campaign Fund in “Part II.”

Explain the reason for filing Form 1040-X in “Part II.”

Sign and date the return. Assemble the return with supporting documents in sequential order under Form 1040-X. Mail Form 1040-X and the supporting documents to the address listed on the form’s instructions.


  • The IRS advises that it can take up to 12 weeks to process your return and distribute your refund.

About the Author

Angela M. Wheeland specializes in topics related to taxation, technology, gaming and criminal law. She has contributed to several websites and serves as the lead content editor for a construction-related website. Wheeland holds an Associate of Arts in accounting and criminal justice. She has owned and operated her own income tax-preparation business since 2006.