How much is missing? The 2 most common reasons this year is you entered the wrong amount on line 30 for the Recovery Rebate Credit (3rd Stimulus payment) or line 28 for the Child Tax Credit. Those lines are just if you didn't already get the full amount or qualify for more. The IRS knows what they already sent you.
A lot of people answered the questions wrong and tried to claim the credits again. Double check your bank statements to see what the IRS sent you during the year for the 3rd Stimulus payment.
NOT TAXABLE
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.
Look at your tax return. It is not added as income anywhere or subtracted anywhere. The Recovery rebate credit on line 30 is only if you didn't get the Stimulus payment or qualify for more.
