Creit card interest is the principal way in which card issuers generate revenue. A card issuer is a bank that gives a consumer (the cardholder) a card or account number that can be used with various payees to make payments and borrow money from the bank simultaneously. The bank pays the payee and then charges the cardholder interest over the time the money remains borrowed. Banks suffer losses when cardholders do not pay back the borrowed money as agreed. As a result, optimal calculation of interest based on any information they have about the cardholder's credit risk is key to a card issuer's profitability. Banks check national, and international if applicable, credit bureau reports that identify the borrowing history of the card holder applicant with other banks, or take detailed interviews and documentation of the applicant's finances, before determining what interest rate to offer.