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# What is a Bank Card Number?

Article Details
• Written By: Lee Prangnell
• Edited By: A. Joseph
• Last Modified Date: 28 August 2019
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On the front of a bank card there exists a long set of numbers typically in the middle of the card, ranging from 12-19 digits, depending on the issuing network of the card. This number is known as the "bank card number." The bank card number follows a standardized numbering system that was enforced by the International Organization for Standardization (ISO). The numbering system is known as ISO/IEC 7812, and it also is utilized on credit cards and other types of identification cards, such as healthcare identification cards.

The "Issuer Identification Number," formerly known as the "Bank Identification Number," is the term used to describe the first six digits of the bank card number. The first six digits identify the financial institution that has issued the card. The details of each institution are stored on a database. The rest of the digits are random and are generated by the financial institution, such as a banking corporation, and are validated against the database using the Luhn algorithm. The Luhn algorithm is mathematical formula that is utilized to validate — to check whether the bank card number is duplicated, for example — different types of identification numbers.

Banks, on a global scale, issue unique cards to their customers. The bank card number is a unique identifier, because a banking institution would never issue the same number to two different customers, which would violate the rules as specified in the ISO/IEC 7812 standards. The main reasons why each bank card has a unique number are because is provides enhanced security, and it makes the transaction process more efficient. If two customers had the same bank card number, complications could occur during the transaction process.

If an individual wishes to make a purchase on the Internet, he or she would be required to make the purchase with a form a payment card, including a bank card. In a typical online transaction form, an individual must enter personal and financial information such as name, address, bank card number, bank card expiration date and the bank card security code. This information will be submitted to a centralized database — in which the user's personal and financial information is stored — for the purposes of security and authorization. If, for example, the bank card number entered in the form does not match the card number in the centralized database, the transaction will be declined. The user will be required to resubmit the form if he or she wishes to purchase the product in question.