The fee paid to the card issuing bank by the card acquiring bank by way of the processor. Interchange is the base fee to which all other acquiring and processing fees are added to come up with the merchant discount rate. Interchange rates vary widely based on card type, transaction amount, risks and retail sector. It is assessed on all Visa- and MasterCard-branded cards, even PIN-based debit cards. In certain circumstances interchange flows in reverse, such as following a chargeback.