If you have discovered a mistake in a tax return that has already been filed, you can file an amended return, also known as Form 1040X. The Internal Revenue Service allows you to amend a return if your filing status is incorrect, your income is wrong, or you have incorrectly calculated deductions or tax credits. The IRS also sets a deadline on correcting an old return with a 1040X.
You indicate the year of the tax return you're amending at the top of Form 1040X. For amended returns, the IRS sets a deadline of three years from the date the original tax return was due. For example, if the due date of the return was April 15, 2010, you have until April 15, 2013, to file a Form 1040X for 2009. If you paid the tax after you filed the return, then the deadline is two years from the date of your payment if that date would be later.
The IRS will allow you to amend a return to increase the amount of your refund. However, the agency requires you to wait until you receive the first refund before filing the amended return. When that refund arrives, you may deposit it and file the 1040X to claim the increase and an additional refund.
Additional Tax Due
Some taxpayers find they've made a mistake that means they owe additional tax. The IRS will correct your tax return if it has the information supporting a change in your tax liability. If it does not have that information, you are well advised to file an amended return as soon as possible and pay the additional tax before the due date (normally April 15 following the tax year, for individuals). If you don't get the additional tax payment in on time, the IRS might levy penalties and interest on the outstanding balance.
Errors and Mailing
If you've made a math error or have not included a W-2, you don't need to file an amended return, as the IRS will correct your mistake and send you a corrected tax statement, along with a bill for any tax due. You must mail amended returns individually, and they must be in hard copy form. The IRS does not accept electronically filed amended returns.
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