Like the OP we had not filed our return yet so this was odd.
We called and were informed that it was indeed a tax refund check, cut against a filed return (Identity theft).
I commented to the guy that it didn't do the thieves much good since the check came to me - he said often it goes to a different address (PO box) put on the return by the perps.
Upshot is, this was prolly a valid check from the government and the OP now gets to jump through the identity theft hoops, plus gets a special ID number from the IRS to validate future returns.
“OP”????