@AlwaysDayDue The IRS should have caught the missing form 6419 and adjusted your return and reduced your refund or sent you a bill. Check your 1040 return line 28. Line 28 is only if you didn't get the Child Tax Credit or qualify for more. Do you remember entering the Advance Child Tax Credit you got? You don't need to add the 6419 if you entered the amount you got without it...
The Advance Child Tax Credit payments should have been $300 per month (July-Dec) for each child under the age of 6 plus $250 per month for each child age 6-17 (based on the children listed on your 2020 tax return, but using their ages as of 12/31/21). If you are married you should have each received a form 6419 for half.
