IRS Form 1120-X (Amended U.S. Corporation Income Tax Return) is used by corporations to correct errors or make changes to a previously filed Form 1120. This form allows corporations to report any changes in income, deductions, credits, or tax liability.

Purpose of Form 1120-X
  • Corrections and Changes. To correct errors or make any changes to income, deductions, credits, or calculations on a previously filed Form 1120.
  • Due Date. A corporation can generally file an amended tax return anytime; however, if the corporation is filing Form 1120-X to request a tax refund, the filing must be submitted within three years from the date the original return was filed, or within two years from the date the tax was paid, whichever is later. Otherwise, the refund claim is barred under the statute of limitations (SOL) and the IRS will not process the refund request.
Information Required
  • Basic Information. The corporation’s name, address, employer identification number (EIN), amended tax year, and the IRS office where the original tax return was filed.
  • Original and Corrected Amounts. Columns A, B, and C on Form 1120-X show the original amounts, net changes, and corrected amounts for income, deductions, and credits.
  • Explanation of Changes in Part II. The corporation must provide a narrative that explains each of the changes and the detailed reasons for the changes.
  • Attach Supporting Documents. Attach any necessary schedules, forms, or documentation supporting the changes that were made to the return. It is customary for corporations to include a full copy of the amended Form 1120 to ensure the IRS has all the information it needs.
Video Tutorials

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Additional Information

Corporations seeking more information on amended tax returns can view the Form 1120-X Instructions.