If a customer has paid, money has left their bank account, but the deposit failed due to QuickBooks being linked to an incorrect bank account, how do I correct it?

Hello there, @monomythproducti.

Allow me to share some information about failed deposits and assist you in how we can correct and handle this.

In QuickBooks Online (QBO), bank transfer payments can fail due to incorrect bank info or insufficient funds. In your case, the customer might've entered the wrong bank info. To handle this in QBO, please follow the steps below:

First, let's figure out where the failed payment is in QuickBooks:

1. Click on the + New icon and select Bank Deposit.
2. Review the QuickBooks Payments section.
3. Locate the payment on this list. If you see it, it isn't deposited yet. If you don't, it is deposited.

Next, let's create a service item to track a rejected bank transfer:

1. Go to the Gear ⚙ icon and select Products and Services.
2. Select New and then Service.
3. Enter "Rejected bank transfer" for the name.
4. Enter "Bank transfer payment received rejected by the bank" for the description.
5. Select the bank account you deposited into for the Income account if the bank deposit is already deposited. Or if you haven't made the bank deposit yet, select Undeposited funds for the Income account.
6. When done, hit Save and close.

Now, we're ready to create a new invoice to record the rejected payment. Recording it keeps your income and A/R accounts accurate:

1. Click on the + New icon and select Invoice.
2. Enter the customer who had the failed bank transfer payment.
3. Add the rejected bank transfer item you created in step 2 to the invoice.
4. Enter the total amount of the rejected payment.
5. Make sure Tax is not selected.
6. Hit Save and close.

Lastly, since the payment didn't go through, we'll need to remove it from the original invoice and move it to the newly created invoice:

1. Open the invoice that has the rejected bank transfer payment.
2. Select the Payment link to open the rejected payment.
3. Uncheck the original invoice, then select the newly created one.
4. Select Save and close.

You can also charge your customer for the failed payment fee, however, it is just optional. 

Moreover, QBO has the option to allow users to find or update Directed Deposit funding time, To know more about this, feel free to browse through this article: View or change your direct deposit time funding time in QuickBooks Online.

I'll be around in case you need further assistance with regard to handling failed deposits in QBO. Simply leave a comment below, and I'll get back to you. Keep safe.