Form 1040m: How to Correct or Amend a Tax Return

While “Form 1040m” is a common search term, it is not an official Internal Revenue Service (IRS) document. The correct form to amend a previously filed U.S. Individual Income Tax Return is Form 1040-X, Amended U.S. Individual Income Tax Return. This form is used to correct mistakes or make changes to your Form 1040, 1040-SR, or 1040-NR after submission. These corrections may result in either an additional refund or a balance due.

When to File an Amended Return

An amended return should be filed to correct significant errors, not for minor mathematical mistakes which the IRS typically corrects during processing. Common reasons to file Form 1040-X include correcting your filing status, the number of dependents claimed, or your total income. You would also file an amendment to claim deductions or credits you omitted on your original return. Generally, you must file Form 1040-X 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 are due a refund from your original return, you should wait until you receive that refund before filing.

Information and Documents Needed

You will need a copy of the original tax return you are amending and any new or corrected informational documents that prompted the change, such as a corrected W-2c or a corrected Form 1099. Any schedules or forms that are affected by the change must also be attached to your Form 1040-X. The form is structured with three main columns: Column A for the figures from your original return, Column B shows the net increase or decrease for each line item, and Column C presents the corrected amounts. You must also provide a written explanation for each change in Part II of the form.

How to Submit Your Amended Return

For recent tax years, you can file Form 1040-X electronically using approved tax software or mail a paper copy. Check the official IRS website for the correct mailing address, as it varies depending on where you live and whether you are including a payment. After submitting the form, you can monitor its progress using the IRS’s “Where’s My Amended Return?” online tool. Processing an amended return can take up to 16 weeks or longer, so the tracking tool is useful for updates.