I have additional bank information. My return is already filed. How can I calculate the impact of the new information?

You can use the TurboTax Amend/Change my Return routine to add things to your tax return to see what impact it has on it. You will see an option for this on your home page when you log into your tax return.

You need to indicate that you want to amend your return for 2020, but once you make your changes you can cancel them if you don't want to proceed with the amendment.