Once again the RRC is based on the 2020 AGI ONLY and not anything from the 2018 or 2019 returns. The program handles this correctly.
When the stimulus payments were sent out in advance the first was based off the 2018 AGI (or the 2019 if filed early enough to catch the cut off date) and the second was based off the 2019 AGI. But when you reconcile this on the 2020 return the RRC uses only the 2020 AGI.
Now the third stimulus advance is based on the 2019 AGI but if you got the payment before you filed the 2020 return and you qualify for more then they are sending out "PLUS UP" payments based on the 2020 AGI. BUT ... if when you file the 2021 return the third stimulus will be reconciled yet again using the 2021 AGI so if you are eligible for more you will get it on the 2021 RRC.
