Why they asking child credit for 2019 to 2021 what happened to 2020

[winterus2000]

Why they gave 1800 but charging 2800

[Critter-3]

You are mixing up apples and oranges ... the same "look back" option is available on the 2021 return to be able to use  the 2019 Earned Income  ( just like it did on the 2020 return)  to see if using the 2019 amount  will get you a bigger CTC and/or EIC on the 2021 return.    Simply follow the screen instructions and you continue thru the program interview. 

[DianeW777]

The reason they use the 2019 tax year earned income is because it is considered 'pre COVID' or pre-pandemic. This was a full year of regular or usual employment. This could potentially create a better credit situation which is why is allowed to be used to determine the best outcome for your situation in regards to the refundable earned income credit (EIC) as indicated by @Critter-3).