The difference between a refund and a credit is that a 'refund' is matched against a sale, whereas a 'credit' is independent of a sale. This means that a refund can only be the same value or lower than the original sale amount, whereas a credit can be for any amount.
Please note a REFUND_SALE can only be attempted on the Gateway up to 365 days following the original SALE's settlement date. Each Acquirer sets their own limit for this, please check with your Acquirer to confirm their limit.
Processing a Refund
Find the transaction you wish to refund under the 'Transactions' tab in the MMS (Merchant Management System) and choose the 'REFUND SALE' option (under the Action column). This will present a dialog box:
Now you can edit the amount which you wish to refund to the cardholder. You can return either the exact or a lower amount to the cardholder.
Once the amount is correct, click 'Refund Transaction' at the bottom of the dialog box.
Processing a Credit
Find the transaction you wish to refund under the 'Transactions' tab and choose the 'VIRTUAL TERMINAL' option (under the Action column). This will re-direct you into the Virtual Terminal.
Change the Transaction Type to 'CREDIT' and edit the amount which you wish to credit to the customer. Then go to the bottom of the page and click 'Process Transaction'. The credit will then be processed.