Do you have a question?
Is the check from the IRS or the U.S. Treasury? Does it say it's an income tax refund?
What is the exact amount of the check? If it's a small amount it might be interest that the IRS is paying you because they were late paying the refund from your tax return. If that's what it is, you have to report the interest as income on your 2025 tax return, just like interest from a bank.
If the check is from the IRS, they should send you a letter explaining why they sent the check. It might be two or three weeks before you get the letter.