On an existing Credit that was entered as an actual credit rather than a refund, the overlay will look something like this:
Once a Credit is entered, the Client field cannot be modified. The Date field is the date the Credit was created for the Client. The Reference # is a required field so the text there may not be necessary. A Line Item must be added to add an amount to the credit. This also allows the Credit to be applied to Invoices.
In the above screenshot, the Credit was added for the "Shrub Trimming" service. Above the line item is a list of Invoices that the Credit can be applied to based on the Line Items on the Credit. If you were to do something like run a promotion that was good for something like "$50 off all scheduled services" then you will probably need to change the Credit later so at least one line item reflects the services the Client would be Invoiced for.
If a Credit was entered manually but the Refund checkbox was selected, there will be some additional fields on the overlay:
Even if an amount is entered in the Refund Amount field, you will still need to enter at least one line item and a rate so the Credit can be applied to Invoices. Refund Payment Method will be the way in which the Client was refunded. If you select a credit card type, this should only be if the actual credit card transaction does not exist in SA. The Refund Reference # will likely be the same as the Reference #. This may be the check number that was sent to the client or the transaction number on a credit card or bank draft transaction.
If a Credit is created as part of a credit card refund, this overlay will look completely different:
Notice the top of the Credit Refund says "Edit Refund". This is a good reminder that this transaction is tied to a Payment Credit and is part of a refund transaction. The Payment Credit and Credit Refund offset each other while the original Payment is still applied to the Invoice even though the refunded amount was subtracted from the Payment Amount. You will notice on this overlay that there is no save button. This transaction cannot be modified once it is created because it is tied to a credit card refund.