I had tax due on Turbotax this year so I paid. Recently I received a federal check for the tax refund. Why do I receive a tax refund when I had tax due (and it was paid?)

Did you have unemployment on the original return ?   If so did  you miss the news story about the late tax law change making up to $10,200 of the unemployment not taxable so the IRS has been recalculating the early filed returns and sending a refund if applicable.  

Oh that's why. Thanks a lot for your answer!