Bank Card Number - Issuer Identification Number (IIN)

Issuer Identification Number (IIN)

The first six digits of a card number (including the initial MII digit) 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. Cards are issued by the issuer through an issuing network. The card number's length is its number of digits. Many card issuers print the first four digits of the IIN on their card, just beneath where the number is embossed, as an added security measure.

In the United States, 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 real-time claims. Each processor has one or more IINs, which it divides into plans by using Group Number and Processor Control Number fields.

The IIN database and membership is managed by the American Bankers Association (ABA) and is updated monthly. The ABA is responsible for allocating IIN ranges to the issuing networks.

Online merchants may use IIN lookups to help validate transactions. For example, if a 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.

On November 8, 2004, MasterCard and Diners Club formed an alliance. Diners Club cards issued in Canada and the United States start with 54 or 55 and are treated as MasterCards worldwide. International cards use the 36 prefix and are treated as MasterCards in Canada and the United States, but are treated as Diners Club cards elsewhere. Diners Club International's web site makes no reference to old 38 prefix numbers, and they can be presumed reissued under the 55 or 36 IIN prefix. Effective October 16, 2009, Diners Club cards beginning with 30, 36, 38 or 39 have been processed by Discover Card.

Effective October 1, 2006, Discover began using the entire 65 prefix, not just 650. Also, similar to the Master Card/Diners agreement, China Union Pay cards are now treated as Discover cards and accepted on the Discover network.

A search on Visa's web site 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 two different schemes were devised for this that included appending three digits to the account number, and, in more rare cases, inserting three digits after the twelfth digit of the old 13-digit number.

Switch was re-branded as Maestro in mid-2007. In 2011, UK Domestic Maestro (formerly Switch) was aligned with the standard international Maestro proposition.