We were able to use $0 to file the 2020 tax return, in which we got the first two stimulus amount in the filing. After IRS processed it and refunded the 2020 amount (took about 2-3 weeks), IRS deposited the 3rd stimulus directly to the same bank account that we put in the 2020 tax filing (took another week).
From our experience, I think as long as IRS has processed your 2020 tax return successfully and refunded the amount, your stimulus record has been updated up till the 2nd stimulus. Therefore they will deposit the 3rd stimulus amount in the next batch process.
