Where to File Your Amended Tax ReturnMail your amendment to the same IRS Service Center that processed your original tax return. If you don't remember where you mailed your return, or if you efiled your tax return, simply mail the amended return to the IRS Service Center shown on pages 4 and 5 of the Instructions for Form 1040X [PDF].
What Happens When You File an Amended ReturnThe IRS Service Center will manually process your amended return. They will check to make sure your explanations are sufficient. They will check to see that you have sufficiently documented the changes in your tax return. For example, they will double check your W-2 statements, withholding, and other information reporting on your amended tax return. If the IRS needs more explanation or documentation, they will write you a letter and ask for the specific information they need. If you owe additional tax, you should mail in a check to pay the tax in full. If you are due an additional refund, expect your refund to arrive in approximately 8 to 12 weeks.
Do Amended Returns Trigger an Audit?There has been discussion among various tax professionals whether an amended tax return will trigger an IRS audit. So far, there's no conclusive evidence. Based on my experience and the experience of other tax professionals, the IRS does check amended tax returns more thoroughly than original tax returns. If you explain the reasons why you are correcting your tax return, and if you back this up with proper documentation, the IRS is likely to process your amended return more efficiently.
For example, let's say you forgot to report the full amount of mortgage interest you could have claimed. You should attach a photocopy of all your 1098 mortgage statements and highlight which one was left off the original return. While the IRS agent could look this information up on their computers, it will be easier and more efficient for them to see the documentation right there in your tax return.
The Bottom LineFiling an amended return is the right thing to do if you need to correct the amount of income, deductions, credits, filing status, or dependents on your tax return. You can amend to claim tax benefits that will result in an additional tax refund, and you can also amend to remove deductions and credits you were not entitled to. In preparing Form 1040X, you need to provide thorough documentation, and clear explanations of your changes.