A chargeback occurs when a cardholder initiates a dispute on a card transaction with their issuing bank. If the bank agrees that the dispute seems valid, it will initiate a chargeback to the merchant and forcibly deduct the amount in question.  From there, the merchant will be notified, and they can either fight the chargeback by providing evidence that the transaction is authorized and legitimate or let the chargeback go through. In either case, the final decision is up to the cardholder's bank, and the merchant is charged a fee for the chargeback regardless of the authenticity of the transaction.