A credit card is part of a system of payments named after the small plastic card issued to users of the system. It is a card entitling its holder to buy goods and services based on the holder's promise to pay for these goods and services. The issuer of the card grants a line of credit to the consumer (or the user) from which the user can borrow money for payment to a merchant or as a cash advance to the user.

A credit card is different from a charge card, where a charge card requires the balance to be paid in full each month. In contrast, credit cards allow the consumers to 'revolve' their balance, at the cost of having interest charged. Most credit cards are issued by local banks or credit unions, and are the shape and size specified by the ISO/IEC 7810 standard as ID-1. This is defined as 85.60 × 53.98 mm in size.

How credit cards work

Credit cards are issued after an account has been approved by the credit provider, after which cardholders can use it to make purchases at merchants accepting that card.

When a purchase is made, the credit card user agrees to pay the card issuer. The cardholder indicates 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/Cardholder 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 and Ireland 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 issuer charges interest on the amount owed if the balance is not paid in full (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, thus avoiding late payment altogether as long as the cardholder has sufficient funds.


Advertising, solicitation, application and approval

Credit card advertising regulations include Schumer's box disclosure requirements. A large fraction of junk mail consists of credit card offers. The three major US credit bureaus (Equifax, TransUnion and Experian) have chosen to allow consumers to opt out from receiving virtually all credit card solicitation offers by mail. It can be done temporarily (via 1-888-5-OPTOUT (1-888-567-8688) or OptOutPreScreen.com and can be made permanent via appropriate reply to a confirmation letter sent by postal mail in response.

Interest charges

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 transaction and repaid it in full within this grace period, there would be no interest charged. If, however, even $1.00 of the total amount 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 (ADB) 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, 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, to encourage balance transfers from cards of other issuers. In the event that several interest rates apply to various balance segments, payment allocation is generally at the discretion of the issuing bank, and payments will therefore usually be allocated towards the lowest rate balances until paid in full before any money is paid towards higher rate balances. Interest rates can vary considerably from card to card, and the interest rate on a particular card may jump dramatically if the card user is late with a payment on that card or any other credit instrument , or even if the issuing bank decides to raise its revenue.

Benefits to customers

The main benefit to each customer is convenience. Compared to debit cards and checks, a credit card allows small short-term loans to be quickly made to a customer who need not calculate a balance remaining before every transaction, provided the total charges do not exceed the maximum credit line for the card. Credit cards also provide more fraud protection than debit cards. In the UK for example, the bank is jointly liable with the merchant for purchases of defective products over £100.

Additionally, carrying a credit card may be a convenience to some customers, as it eliminates the need to carry any cash for most purposes.

Detriments to customers

High Interest and Bankruptcy

Credit cards with low introductory rates are limited to a fixed term, usually between 6 and 12 months after which a higher rate is charged. As all credit cards assess fees and interest, some customers become so encumbered with their credit debt service that they are driven to bankruptcy. Credit cards will often stipulate a default rate of 20 to 30 percent in the event a payment is missed. That is, if a consumer misses a payment, the rate will automatically increase to a very burdensome level. The practice of universal default, in which the deafault rate is applied to a card in good standing merely by missing a payment on an unrelated account, greatly magnifies this harm. This can lead to a snowball effect in which the consumer is drowned by unexpectedly high interest rates. Further most card holder agreements enable the issuer to arbitrarily raise the interest rate for any reason they see fit.

Inflated Pricing for All Consumers

Merchants that accept credit cards must pay interchange fees and discount fees on all credit-card transactions. However, merchants are usually barred by their credit agreements from passing these fees directly to the credit card customers, or from setting a minimum transaction amount. The result, at least in the United States, is that even consumers that do not use credit cards experience higher prices to cover the hidden transaction fees afforded for credit cards. In the United States in 2008, credit card companies collected a total of $48 billion in interchange fees, or an average of $427 per family, with an average fee rate of about 2% per transaction. Since these fees can't be passed directly to credit card customers, they become a hidden part of the prices offered by any merchant to all of its customers.

Grace period

A credit card's grace period is the time the customer has to pay the balance before interest is assessed on the outstanding balance. Grace periods vary, but usually range from 20 to 50 days depending on the type o

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