A credit card is a system of payment named after the small plastic card issued to users of the system. A credit card is different from a debit card in that it does not remove money from the user's account after every transaction. In the case of credit cards, the issuer lends money to the consumer (or the user) to be paid to the merchant. It is also different from a charge card (though this name is sometimes used by the public to describe credit cards), which requires the balance to be paid in full each month. In contrast, a credit card allows the consumer to 'revolve' their balance, at the cost of having interest charged. Most credit cards are the same shape and size, as specified by the ISO 7810 standard. How credit cards work:$ A user is issued credit after an account has been approved by the credit provider, and is given a credit card, with which the user will be able to make purchases from merchants accepting that credit card up to a pre-established credit limit. Often a general bank issues the credit, but sometimes a captive bank created to issue a particular brand of credit card, such as Chase, Wells Fargo or Bank of America issues the credit.When a purchase is made, the credit card user agrees to pay the card issuer. The cardholder indicates their consent to pay, by signing a receipt with a record of the card details and indicating the amount to be paid or by entering a Personal identification number (PIN).Also, many merchants now accept verbal authorizations via telephone and electronic authorization using the Internet, known as a Card not present (CNP) transaction. Electronic verification systems allow merchants to verify that the card is valid and the credit card customer has sufficient credit to cover the purchase in a few seconds, allowing the verification to happen at time of purchase. The verification is performed using a credit card payment terminal or Point of Sale (POS) system with a communications link to the merchant's acquiring bank. Data from the card is obtained from a magnetic stripe or chip on the card; the latter system is in the United Kingdom commonly known as Chip and PIN, but is more technically an EMV card. Other variations of verification systems are used by eCommerce merchants to determine if the user's account is valid and able to accept the charge.These will typically involve the cardholder providing additional information, such as the security code printed on the back of the card, or the address of the cardholder.Each month, the credit card user is sent a statement indicating the purchases undertaken with the card, any outstanding fees, and the total amount owed. After receiving the statement, the cardholder may dispute any charges that he or she thinks are incorrect (see Fair Credit Billing Act for details of the US regulations). Otherwise, the cardholder must pay a defined minimum proportion of the bill by a due date, or may choose to pay a higher amount up to the entire amount owed. The credit provider charges interest on the amount owed (typically at a much higher rate than most other forms of debt). Some financial institutions can arrange for automatic payments to be deducted from the user's bank accounts.Credit card issuers usually waive interest charges if the balance is paid in full each month, but typically will charge full interest on the entire outstanding balance from the date of each purchase if the total balance is not paid. For example, if a user had a $1, 000 outstanding balance and pays it in full, there would be no interest charged. If, however, even $1.00 of the total balance remained unpaid, interest would be charged on the $1, 000 from the date of purchase until the payment is received. The precise manner in which interest is charged is usually detailed in a cardholder agreement which may be summarized on the back of the monthly statement. The general calculation formula most financial institutions use to determine the amount of interest to be charged is APR/100 x ADB/365 x number of days revolved. Take the Annual percentage rate (APR) and divide by 100 then multiply to the amount of the average daily balance divided by 365 and then take this total and multiply by the total number of days the amount revolved before payment was made on the account. Financial institutions refer to interest charged back to the original time of the transaction and up to the time a payment was made, if not in full, as RRFC or residual retail finance charge. Thus after an amount has revolved and a payment has been made that the user of the card will still receive interest charges on their statement after paying the next statement in full (in fact the statement may only have a charge for interest that collected up until the date the full balance was paid...i.e. when the balance stopped revolving). The credit card may simply serve as a form of revolving credit, or it may become a complicated financial instrument with multiple balance segments each at a different interest rate, possibly with a single umbrella credit limit, or with separate credit limits applicable to the various balance segments. Usually this compartmentalization is the result of special incentive offers from the issuing bank, either to encourage balance transfers from cards of other issuers, or to encourage more spending on the part of the customer.