It happens but it is certainly rare. The treasury sends the check and the IRS should also send an explanation, but they arrive in different envelopes. The IRS has probably credited you with more withholding, or they determined you qualified for a deduction or credit you didn't take. I would wait until you get the explanation and have a chance to decide whether the IRS is correct or not before spending the money. If the correcting the IRS made turns out not to be correct, you will return the money and find a way to correct your file with them. We can help with advice on that once you know what the change was that resulted in this refund.
