I'll proceed under the assumption this answer is correct and that by entering amounts for the 2nd stimulus check on the 2020 return is responsible accounting. I haven't proceeded with this assumption yet am reserving final judgment as it's possible the 2nd stimulus amount has not been received prior to the filing of the 2020 return. What does the program do in that case? I guess I'll find out once I have a client who hasn't received the 2nd stimulus amount.  And finally....I guess Covid19 (would call it another name but don't want to be kicked out of this forum) even "trumps" generally accepted accounting....cash basis t/p's report or account for income when actually received.  But again, I may be jumping the gun with this assumption.

But anyway thanks for the info.

I personally received my 2nd stimulus payment in January 2021. It was direct deposited into bank account by IRS. So do we put on 2020 return or 2021? 

Aren't taxpayers on a cash basis? Thus 2021? 

2020 return. Check the worksheet instructions. The software has a place to enter both payments, too.

Not everything is cash basis. If you made a 2020 estimated tax payment on 1/15/21  that goes on the 2020 return, as will a 2020 extension payment or IRA contribution made on 4/15/21