How much is missing? If the IRS adjusted your return they will mail you a letter.
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 and Check your IRS account (both accounts if married)
Your Online Account | Internal Revenue Service
