The Recovery Rebate Credit on the 2020 federal tax return is based on your 2020 AGI.
Yes -- it is based on your 2020 income.
The stimulus check is an advance on a credit you can receive on your 2020 tax return. If something went wrong or you did not get the stimulus check in 2020, you can get it when you file your 2020 return in early 2021
The Recovery Rebate Credit will be found in the Federal Review section, If you are eligible it will end up on line 30 of your 2020 Form 1040.
https://ttlc.intuit.com/community/tax-topics/help/how-will-the-stimulus-package-impact-me/00/1393859
good post with screen shots for recovery rebate credit
I had two dependents on my 2019 Tax Return who were eligible dependents for purposes of my second EIP. I will only have one of them eligible on my 2020 Tax Return,
However, I did not receive a check yet in the mail and according to the error message at Get My Refund I will now not get one (mine was not mailed out in Jan. 2021). So, now, I have to claim the Recovery Rebate Credit on my 2020 tax return.
In doing so, the IRS will now issue my RRC based on my 2020 return instead of on my 2019 return, which it shoudl have done. That means I will be cheated out of $600 on my second EIP
Unfair!