Refunding Fees to Client when client was "overbilled" and client paid fees they should not have paid

The best way to do this is to find the Invoice that contains the "Fees" that were paid by the client and reverse the payment applied against it. When the payment reversal is done, choose not to delete the original transaction so that the payment can be used later.  After the  payment reversal is done, go ahead and write off the amount using the WO code that should not have been paid by the client (use the same amount as the refund), apply against the Invoice and post. After posting the WO, re-apply the payment that was reversed earlier against the remainder of the Invoice.  This will come up with a remaining balance since you have already written off part of the Invoice.  Go ahead and post the payment as "partially applied" which will put the remainder into "Retainer" automatically as RDP.  The retainer balance can now be used to refund money paid by the client for fees through going to AP Manager > Voucher Processing and using the RDS code.