What Is Amending Taxes? How and When to File

An amended tax return is an official tax form submitted to the Internal Revenue Service (IRS) to correct errors or omissions on a previously filed tax return. This process allows taxpayers to adjust inaccurate or incomplete information, rectifying mistakes that may have led to an overpayment or underpayment of taxes. Filing an amended return ensures your tax records accurately reflect your financial situation for a given tax year.

When to File an Amended Return

Filing an amended tax return is necessary when information on the original return was incorrect. This includes misreported income, overlooked deductions, missed tax credits, or an incorrect filing status. For example, you may need to amend if you filed as single but were eligible for head of household.

You might also need to amend if you receive new tax documents, like a corrected Form W-2 or 1099, after your original return was submitted. An amended return is not typically required for mathematical errors, as the IRS usually identifies and corrects these automatically during processing and will notify you of any adjustments.

Generally, you have a specific timeframe to file an amended return: within three years from the date you filed your original return, or within two years from the date you paid the tax, whichever is later. If you filed your original return before the annual tax deadline, the three-year period begins from the tax deadline itself. Special circumstances, such as a federally declared disaster or bad debts, may extend this period.

Completing Your Amended Federal Tax Return

To correct a previously filed federal individual income tax return, use Form 1040-X, Amended U.S. Individual Income Tax Return. Before starting, gather a copy of your original tax return, any new or corrected tax forms (such as W-2s or 1099s), and supporting documents relevant to the changes.

Form 1040-X is structured with three columns to facilitate the amendment process. Column A is for amounts from your original tax return. Column B is where you enter the net increase or decrease for each changing line item. Column C shows the corrected amounts, which are the result of adding or subtracting Column B from Column A.

Part III of Form 1040-X requires a clear and concise explanation for each change. Provide specific details, for example, “Adjusted gross income on line 1 decreased by $2,000 due to omitted business expenses on Schedule C.” If changes relate to items on a schedule, prepare a new or corrected schedule and attach it to your Form 1040-X.

Submitting Your Amended Return and What Happens Next

After completing Form 1040-X and attaching all necessary supporting documentation, such as corrected W-2s or 1099s, submit your amended return to the IRS. While some tax software allows electronic filing for recent tax years, paper filing by mail remains a common method, especially for older tax periods or specific circumstances.

If you are mailing your amended return, send it to the specific IRS address that varies based on your geographic location. Consult the IRS instructions for Form 1040-X or the IRS website to find the correct mailing address for your area. If you are amending returns for multiple tax years, mail each in a separate envelope for proper processing.

Once the IRS receives your amended return, processing generally takes between 8 to 12 weeks, though it can extend up to 16 weeks in some cases. You can track its status using the IRS’s “Where’s My Amended Return?” online tool, typically three weeks after submission. If you owe additional tax, pay it by the original tax due date to avoid potential penalties and interest. If a refund is due, the IRS will issue it after processing.