Refunding using full card data means that you are able to enter the patron's credit card in full and ask for a refund. You should receive an authorization.
Refunding with no previous card on file requires:
You cannot do mass refunds unless you have card data (or a merchant profile) stored in the database. If you find that you need to refund a lot of people and have neither, you can still use the mechanisms described in refunding to an entire performance
Since you have to be talking to a patron to refund money when typing in the full card data, you are able to ask them for their card data.
Typical issues that can arise are: