I know this is an old thread, but . . .
In 2012 I was going through a lot of upheaval in my life and over paid a lot in estimated taxes since my earnings ended up being much less than anticipated. I filed my tax return before April 15th 2013 and forgot about it. In 2015 I received a check from the IRS for the amount of my refund plus interest with no explanation. As I said, I forgot about my refund and thought the check was a mistake so I called the IRS. There still was no explanation, but they did confirm that the check was legitimate as it was a refund from 2012.
