The stimulus checks are an advance on a credit you can receive on your 2020 tax return. If something went wrong or you did not get either the first or second stimulus checks the you can get it when you file your 2020 return in early 2021—if you are eligible. It will end up on line 30 of your 2020 Form 1040.
https://www.irs.gov/newsroom/economic-impact-payment-information-center-topic-j-reconciling-on-your-...
https://www.irs.gov/coronavirus/coronavirus-tax-relief-and-economic-impact-payments-for-individuals-...
https://ttlc.intuit.com/community/tax-topics/help/how-will-the-stimulus-package-impact-me/00/1393859
At this point, we don't know how long the new stimulus bill means in terms of time to change the 2020 Form 1040, software programming, software updates, etc., etc. Do NOT be in a hurry to file your 2020 tax return until more is known. It is never a good idea to file early, and it would be especially foolish to file an early 2020 return.
