To clarify: You invoice someone for $500. For reasons known only to them, they pay you $600. You clear the invoice and apply the $100 as unapplied cash, to be refunded. To make the refund you can't, as far as I can see, generate the refund payment directly in receivables. If you can, I would like to know how to do it. At present we create an adjustment note in receivables, then create a customer in payables for the single payment. Since we make refunds fairly regularly we end up with a lot of vendors in payables with only one payment. I'm sure I've come across systems where you can generate a refund directly from receivables.