@sanhaight
It is not taxable and you aren't paying it back. Your 2021 return starts out by assuming you didn't get any Stimulus payments so it gives you credit for the full amount and your refund was too high. Then near the end you enter how much you actually got so it only gives you the difference if any. So you don't get it again.
Make sure you enter the amounts you actually got for the 3rd stimulus so you don't claim it again. Check over your return before you file. Make sure line 30 is blank or the extra amount you did not get. Line 30 is only if you didn't get the full amount or qualify for more.
If you have an amount on line 30 but you already got the Stimulus payments it will delay your return. The IRS will take it off and send you a bill.
