Refund customer, but not have it show as an unpaid portion of invoice.

valeriem

My example: I billed a client for maintenance which they paid in full. A couple of months later they decided to use a different service and I agreed to refund them for the unused months. I tied an expense to the initial invoice as a refund, however it is showing the refund amount as an unpaid portion of the invoice. The software is still expecting that payment. How can keep that expense tied to the invoice as a refund but not show it as an unpaid balance?