How to do a credit card refund when there's no balance

Q. I entered a credit card payment on the wrong reservation, and need to do a refund.  However it has a $0.00 balance and won't allow the Refund.

A. The easiest way to do this is to enter a Credit transaction for the same amount, so it has a credit balance.  Then you can do the Refund to refund the credit card, and finally Delete the Credit transaction.  Make sure that if it automatically added a "Deposit Applied" transaction with the Credit, delete that also.