How to Re-file Old Taxes
When you “re-file” old taxes, you’re really just amending an old return. Amendments can be made for several years prior. It is not suggested to amend returns more than 3 years old as it can trigger an audit. 
Form 1040X
Form 1040X is two pages long. It cannot be filed electronically. Use pencil first, and when you are sure that your figures are correct, go over the return in pen. Make sure that you have the right address for the IRS branch that the form needs to be mailed to and send it with delivery confirmation.
Be Prepared to Pay Back Interest
Almost every amended tax return is going to be subject to some kind of back interest. Even amended returns in a current tax filing year can be subjected to interest payments. Set aside enough to be prepared for the interest, or make arrangements to pay the balance within a specific amount of time.
Amend the Right Return
It is a common mistake to amend the wrong year’s return. Make sure that you are amending the right year as you file for earnings of the previous year. If a document shows 2012 earnings, you will amend your 2013 return.
Conclusion
As with any tax return, when you are re-filing an old return, it is important to double and triple check your numbers. It is also important to know that you may be subjected to an audit simply for the amendment, especially if it is one of a substantial amount.
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