IRS Form 1040-X, also known as the Amended U.S. Individual Income Tax Return, is filed by taxation entities to amend an annual tax return that has already been submitted to the IRS. All changes and corrections must be material to the original tax return in order to be approved by the Internal Revenue Service (IRS). This form should be used to correct mistakes that were made on the original tax return that were not solely mathematical, as those types of calculated errors are typically amended through the filing of the original tax return.

Form 1040-X should be submitted within three years of the original return filing or within two years of the tax payment, whichever is later. If the filing is within the time frame determined as applicable by the IRS and the applicable corrections are approved, a taxpayer may receive a refund as a result of the amendment process.

For those taxpayers who e-filed their original return, they are allowed to e-file Form 1040-X as well; otherwise, the amended return must be filed via traditional mail. In the chance that one is filing the correction form, it is important to include any supporting documentation of the changes, whether new or already in the possession of the IRS, along with the filing.

Once the IRS makes a decision on the amended return, they will notify the taxpayer in writing of their decision. The taxpayer must still pay all taxes, penalties, and interest due, if applicable; they will not be applied towards any refund figure that is deemed to be due from the revised filing.

In conclusion, filing IRS Form 1040-X is required when a taxpayer needs to amend an annual tax return that has already been filed with the Internal Revenue Service. Supporting documents for the amendments and any additional assertions that the taxpayer may make in relation to the filing must be included with the form, as must the taxes and interest due (should they be applicable). If the amendment filing is within the timeframe established by the IRS, a taxpayer may find themselves entitled to a refund.