How to Amend a Tax Return After Filing

An amended tax return is a form filed to correct mistakes on a federal income tax return that has already been submitted. Its purpose is to report changes to income, deductions, credits, or filing status. Filing an amendment allows taxpayers to fix errors and ensure they have paid the correct amount of tax, potentially resulting in a refund or an additional tax liability.

Deciding Whether to Amend a Return

The decision to amend a tax return hinges on the nature of the error. An amendment is necessary for significant changes, such as discovering unreported income from a Form W-2 or Form 1099, realizing you are eligible for deductions or credits you failed to claim, or needing to correct your filing status. For instance, if you find receipts for substantial charitable donations or medical expenses that were omitted, filing an amendment would be appropriate.

Not all mistakes require a formal amendment. The IRS often corrects mathematical or clerical errors automatically. If you made an addition or subtraction mistake, the agency will likely catch it and send you a notice with the correction. If you forgot to attach a Form W-2 or a specific schedule, the IRS will send a letter requesting the missing documents rather than requiring a full amended return.

The statute of limitations is a factor in the decision. You have three years from the date you filed your original return or two years from the date you paid the tax, whichever is later, to file an amended return to claim a refund. If you filed your original return before the April due date, the three-year period starts from that deadline.

Information and Documents Needed to Amend

You will need a complete copy of the original tax return you are amending. You must also have any new or corrected informational documents that prompted the change, such as a corrected Form W-2c, a late-arriving Form 1099 for freelance income, or records supporting a newly discovered deduction.

The central document for this process is IRS Form 1040-X, Amended U.S. Individual Income Tax Return. The most current version of Form 1040-X can be downloaded directly from the IRS website to ensure you are using the proper document for the correct tax year.

The form uses a three-column structure to show the changes being made. Column A requires you to enter the figures as they appeared on your original return. Column C is for the corrected amounts after accounting for the changes, and Column B is where you will show the net increase or decrease between the original and corrected figures.

In the “Explanation of Changes” section, you must provide a clear narrative explaining each change you are making and the reason for it. For example, you might write, “Received a corrected Form W-2c from my employer, which increased my reported wages,” or “Amending to claim the American Opportunity Tax Credit, for which I was eligible but did not claim on my original return.”

The Filing Process for an Amended Return

Once Form 1040-X is complete, you can submit it to the IRS. For certain tax years, if the original return was filed electronically, you may be able to e-file the amended return using tax software. The alternative is to file a paper return by mail.

When mailing the amended return, you should include the signed Form 1040-X at the front. Attach copies of any new or corrected forms or schedules that support the changes made. For example, if you are amending your itemized deductions, you would attach a new Schedule A. Do not send original supporting documents, only copies. The correct mailing address for your Form 1040-X depends on your geographic location and is available on the IRS website.

Allow 8 to 12 weeks for the return to be processed, though it could take 16 weeks or longer. You can monitor the status of your amendment online through the IRS “Where’s My Amended Return?” tool, starting three weeks after you file. If the amendment results in a refund, you can choose to receive it via direct deposit for electronically filed returns or as a paper check. If you owe additional tax, it is best to pay it as soon as possible to minimize interest and penalties.

Amending a State Tax Return

Correcting your federal tax return often creates a corresponding need to amend your state tax return. Because most state income tax calculations begin with figures from your federal return, a change at the federal level will impact your state tax liability. Failing to amend your state return can lead to notices, penalties, and interest from your state’s tax agency.

Each state has its own distinct tax system, separate from the IRS. States have their own specific amendment forms and procedures for filing them. To find the correct form and instructions, you must visit the website for your state’s department of revenue or taxation.