How were you given an amount to claim? Did you get a IRS letter 6475?
If you didn't get the 3rd Stimulus payment based on your 2020 return (but should have) and now your 2021 income is too high then sorry you don't qualify for the Recovery Rebate Credit on line 30. You can't get it. The 3rd Stimulus payment is really based on your 2021 return. They just used 2020 to send it out fast.
