From the IRS:
How do I find out if the IRS is sending me a payment?
People can check the status of both their first and second payments by using the Get My Payment tool, available in English and Spanish only on IRS.gov. The tool is being updated with new information, and the IRS anticipates the tool will be available again in a few days for taxpayers.
How will the IRS know where to send my payment? What if I changed bank accounts?
The IRS will use the data already in our systems to send the new payments. Taxpayers with direct deposit information on file will receive the payment that way. For those without current direct deposit information on file, they will receive the payment as a check or debit card in the mail. For those eligible but who don’t receive the payment for any reason, it can be claimed by filing a 2020 tax return in 2021. Remember, the Economic Impact Payments are an advance payment of what will be called the Recovery Rebate Credit on the 2020 Form 1040 or Form 1040-SR.
You cannot change your checking information until you file your 2020 tax return, at which time it will be updated. You can apply for your stimulus payment on that return. You will see questions about it when you go through the Review process in TurboTax, after you enter all of your tax information.