I can't find a way to post a return payment to a customer, for which we have made a credit note. I am in FA 2.3.19 - I can't remember to have seen this problem before updating, but as the operation is not very frequent, I may be wrong.
The case is the following: A customer has been invoiced twice and has paid twice for the same service. Detecting the error, we have made a credit note and reversed his payment with credit card. We now have a problem posting this operation.
The client's balance is of course negative (in his favour), and I need to post a payment from our bank account to his account in our system. When I go to "payments" and choose "customer" and the specific customer, and then put in the amount we have returned, I get the error message "Settled amount have to be positive number." If I try to put the amount in with a negative sign it says "Invalid amount or amount less than zero". If I try in "Allocate Customer Payments or Credit Notes", the credit note pops up, stating correctly that we owe him the amount, but if I try to allocate it, I get the message "nothing to allocate".
Of course I can simply make a posting against customers' payables and our bank account and our general ledger will be OK. But the customer will always appear as if we are owing him the amount.