I already did my taxes but I want to update my bank account before they send the refund.

Once your return has been accepted by the IRS and/or the state, it is not possible to update your bank account. What will happen is that they will send the funds to the account shown on your return. If the account is closed, the bank will reject the funds. Once the funds bounce back, the IRS and/or the state will mail a paper check to the address shown on the return. This normally delays the refund by a few weeks.