Using the current accounts principles and system refunding money to a client should be as simple as entering the amount with a negative sign into the payments systemNot all the eroneous and labour intensive form filling out all for a simple overpayment/refund no matter what type of transaction with the client.
If a client pays for an invoice by direct debit $100.00 too much.We make negative payment -$100.00 received from the client against the invoice, which will reduce the Client account balance from $100 credit to zero. We then make a physical payment to the client by the same method they paid ie bank, credit card etc.
The simple part is, it actually works very well, but with this system, amounts less than zero are not allowed to be entered.
Implimenting this process will require someone to step out of the box and look at the time and user frustration saved.