What It Is:

An amended return   is a Form 1040X filed by a taxpayer to correct mistakes made on a Form 1040, Form 1040A, Form 1040EX, Form 1040NR or Form 1040NR-EZ (U.S. Individual Income Tax Return) filed in the previous three years.

How It Works/Example:

Let's assume you submit your Form 1040 on April 15 and then discover that you made a mistake in your filing status, your income, your dependents, or your deductions. To correct the error, you can file a Form 1040X (Amended U.S. Individual Income Tax Return)--also called an amended return  .

In general, taxpayers have two or three years from the date of their original return to revise their returns, depending on their circumstances. It is not possible to submit corrections for varwrite-downs years on one form, each correction must be submitted individually and in its own envelope, and it is not available electronically at the moment. Taxpayers may amend amended returns.

Why It Matters:

It is important to note that the taxpayer may also need to revise his or her state tax return after revising a federal return.

Additionally, the IRS typically catches simple math errors while processing the return and may contact a taxpayer if a required schedule is missing, it does not catch every problem right away. Even in this scenario, taxpayer may be liable for penalties and accrued interest . Filing an amended return   as quickly as possible is the easiest and cheapest way to make things right.