Method #1. Issue a debit memo or invoice equal to the amount of the credit.

Method #2. Do a -0- cash receipt and specify for negative discount for the invoices in question. Note that you may want to do a general journal entry to move the resulting credit on the g/l to a more appropriate account.

As an alternate to Tom's Method #2, you can do a -0- cash receipt and "pay" the whole credit amount. Then add a GL line, specifiy the GL to which you want the amount to go, and make sure the payment amount matches the credit "payment" amount to offset it. That's one step Write Off instead of needing a journal entry.

Thumbs up to Hyanaga. This is what I love about this forum. People coming up with simple solutions that we may not have thought of before and sharing them.