

On Form 1040X, you should explain why you are submitting an amended return. You should make sure to collect documents that support the basis for the amendment. You will need to submit Form 1040X if you want to amend your return.

The IRS will automatically correct those mistakes and notify a taxpayer about any adjustments. You do not need to file an amended return if you made a mistake in your math. You should simply tell the agent conducting the audit about the mistake and explain why it happened. If an audit is already underway, however, you should not amend your return at that point. This can shield you from most or all of the interest and penalties that the IRS might require you to pay if they audit your inaccurate return and find the mistake.

You can file an amended tax return within three years after filing an inaccurate return. However, a taxpayer in this situation generally does not need to worry if they made an innocent mistake. This might involve forgetting to report a certain income source, wrongly claiming a deduction that did not apply, or failing to claim a deduction that did apply, among other examples. Some taxpayers panic when they discover that they made a mistake on a tax return that they already filed.
