After the 2015 tax season, the IRS sent me a bill for my 2014 tax (because I made an amendment), which I paid immediately.
A few days later, a check from the IRS for my 2015 arrived, which I deposited.
Finally, an IRS letter arrived explaining that they already deduced the amount I owed on my 2014 tax from my 2015 refund check, meaning that I shouldn't have paid the 2014 bill.
Given that I did, would they notice and refund me that amount or do I need to contact them and ask for it?