Agent Certificates allow the generation of certificate/voucher batches without the need for full PDF certificates/vouchers to be sent to a series of guests - rather they can be supplied with certificate/voucher number & validation code to be used in front end via checkout.
When needing to transfer value of order or booking to a certificate/voucher, using Gift Transfer payment type helps track this transfer in system and reporting.
The process of refunding postage paid where certificate has been changed to 'Email' delivery method (or where complimentary refund of postage is to be applied).