Time Limit on Refunds
There is a statute of limitations on refunds being claimed on amended returns. In general, if a refund is expected on an amended return, taxpayers must file the return within three years from the due date of the original return, or within two years after the date they paid the tax, whichever is later.
Returns filed before the due date (without regard to extensions) are considered filed on the due date.
Robert's 2011 tax return was due April 16, 2012. He filed it on March 20, 2012. He wants to amend his 2011 return, expecting the correction to result in a refund. If he gets it postmarked on or before April 15, 2015, it will be within the three-year limit and the return will be accepted. But if the amended 2011 return is postmarked after April 15, 2015, it will fall outside the three-year period and he will not receive the refund.