It is possible to repay an invoice via EFT (direct debit) in BRP. This may be relevant if, for example, a subscription has been charged by mistake and money has been deducted from the customer's account which is now due to be refunded.
Start with crediting the invoice:
Go to Back Office > Persons > Find the customer
Click on the "Finance" tab and make sure the customer still has a valid EFT-authorization
Click on the "Invoices" tab
Mark the invoice which the customer shouldn't have paid > Click on "Credit"
Make sure that the "Credit the originial invoice" box is checked
Since the invoice was already paid, it will now show a negative amount under "Left to pay"
Change the due date on the invoice to a date at least 3 days ahead
Mark the original invoice with a negative amount left to pay > Click on "EFT"
Confirm by clicking "Yes"
The money will now be refunded to the same account registered on the customers EFT authorization.