BANK CARD NUMBER

The numbers found on credit cards and bank cards have a certain amount of internal structure, and share a common numbering scheme. Credit card numbers are a special case of ISO/IEC 7812 bank card numbers.

An ISO/IEC 7812 number contains a single-digit Major Industry Identifier (MII), a six-digit Issuer Identification Number (IIN), an account number, and a single digit check sum calculated using the Luhn algorithm. The MII is considered to be part of the IIN.

The term "Issuer Identification Number" (IIN) replaces the previously used "Bank Identification Number" (BIN). See ISO/IEC 7812 for more information. The card number's prefix is the sequence of digits at the beginning of the number that determine the credit card network to which the number belongs. The first 6 digits of the credit card number are known as the Issuer Identification Number (IIN). These identify the institution that issued the card to the card holder. The rest of the number is allocated by the issuer. The card number's length is its number of digits. IINs are also used in NCPDP pharmacy claims to identify processors, and are printed on all pharmacy insurance cards. IINs are the primary routing mechanism for realtime claims. Each processor has one or more IINs, which it divides into plans by using Group Number and Processor Control Number fields.

Online merchants may use IIN lookups to help validate transactions. For example, if the credit card's IIN indicates a bank in one country, while the customer's billing address is in another, the transaction may call for extra scrutiny. A search on VISA's website results in many references to card numbers being 16 digits long. However, searching for references to 13-digit cards will turn up no results. All 13-digit account numbers have since been migrated to 16-digit account numbers. At least 2 different schemes were devised for this which included postpending 3 digits to the very end of the account number, and, in more rare cases, inserting 3-digits immediately preceding the (former) final 3-digits (of the old 13-digit number).