BOTH 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 the stimulus check this year, you can get it when you file your 2020 return in early 2021—if you are eligible for will end up on line 30 of your 2020 Form 1040.
NEWS JUST OUT ... the second stimulus direct deposit payments will stop going out 1/15 and if you do not get it by then it will be added to the same line 30 as the first stimulus check. Since the IRS will not start processing returns until 1/27 at the earliest NO ONE should try to file prior to that date. By then you will know if the direct deposit was successful and if it is not then the money will be on the 2020 tax return. Don't be in a big rush this year as there are bound to be glitches early in the season with these last minute programming changes.
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-...
