i see this old reply of @lubos, however, i’d like to insist on the option on voiding the transaction.
issuance of a credit note is best when there is tax involved, movement of inventory involved, or perhaps, simply because you have a mutual understanding with the customer and that you are required to do a refund related to the invoice.
however, on some cases which do not involve the above stated scenarios, i.e. incorrectly doing the invoice and that instead of issuing a credit note, it is better to have it cancelled/voided, in order to maintain the sequence on reference number, and to better see perhaps the history of the invoice.
i hope this get’s into the developer’s consideration.