This article applies to Classic Commerce. (Looking for Contextual Commerce documentation?)
Sometimes a customer might contact you to ask about a charge which appears on their credit card, even when the order itself was cancelled, failed, or was rejected for whatever reason. The charge that the customer sees associated with that order is a pre-authorization charge. A pre-authorization is a temporary hold of the available balance on a credit / debit card and they are not responsible for paying for it. The hold is an action of the customer's credit card company, and you / we have no control over whether customer's credit card issuer decides to use this process. The charge will drop off their card within 5-10 business days. The exact timeframe varies with each card issuer and each card issuer has control over when those charges will be dropped or voided.