Was that the letter 6475? No you didn't pay any tax on it. The letter was just telling you it isn't taxable. There is nothing you need to do or get back. Did you get your whole refund or did the IRS reduce it?
How or where do you think it was taxed? Look at your tax return. It is not added as income anywhere or subtracted anywhere. Income is only on 1040 lines 1-11. The Recovery rebate credit on line 30 is only if you didn't get the Stimulus payment or qualify for more. Do you have anything on line 30?
