The first stimulus checks were sent out in 2020. If you received the full amount, you got $1200 for each spouse and $500 for each child under the age of 17. The second checks went out in late 2020 and early 2021---for $600 per spouse and $600 for a child under the age of 17. The recovery rebate credit asks you if you received the amounts for those two rounds of checks. If you received them you have to say yes that you received them.
Until you say yes that you received the checks....the software is putting the checks into your refund as if you did not get them. When you tell the software that you got the checks, it takes the stimulus money out---because you cannot get it twice.
None of this has anything to do with the 3rd stimulus check for $1400. That is a separate check and there is no place to put anything about it on your 2020 return.
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
