If you need to reverse a transaction and refund a customer's credit card, this is how to reverse it:

1. Open up the Invoice that you need to reverse.
2. Press Checkout button once you have reversed all the necessary items.
3. Make sure you have the correct person showing as "Invoiced" and that the Partial payment box has the same negative amount as the shopping cart does. 
   NOTE: Not all employees will be able to see the "Partial Payment" box at the bottom of the page. You must have Customer Credit authority in Employee Authorizations.
   
4. Choose whether or not you want to e-mail the receipt to the customer. Check the box if you do not want to send them a receipt.
5. Write a payment note under the Optional Information section, saying what happened.
6. Type in the credit card number for the customer (in the same manner as if you were taking a payment from them).
7. Hit Submit Payment button