On the TurboTax web portal, when you register for the stimulus check, the portal actually sends a 0 income tax return to the IRS so that your bank information can be used by the IRS to direct deposit your stimulus payment. If you later find out that you have income and have to file a tax return, you'll have to amend that 0 income tax return.
So, if you have filed a 2019 return and did not provide your bank information, you should the IRS portal which will be ready in the next few weeks.
According to the IRS:
The IRS does not have my direct deposit information. What can I do?
In the coming weeks, Treasury plans to develop a web-based portal for individuals to provide their banking information to the IRS online, so that individuals can receive payments immediately as opposed to checks in the mail.