When you (the shop owner) make an authorization, there will be created a reservation for the relevant amount on the cardholder’s bank account.
When you then complete the transaction and charges the amount on the cardholder’s account, the reservation will be removed, usually within 24 hours. Sometimes more.
If you wish to cancel the transaction after the authorization has been placed you can do so by making a void.
Authorizations might be rejected with an error message. If this happens, you should be able to make a new authorization.
A reservation might still appear on the cardholder’s bank account, even though the authorization was rejected. Most of the times this reservation will be released by itself within 24 hours. However, if this doesn’t happen, you can send a confirmation to the cardholder when you have received the funds for the transaction. The cardholder can then go to their bank, and get the reservation removed.