The credit card industry card providers actually get along with each other sufficiently to use a singular system of numbering and processing. It is very similar to the systems used by other industries like department stores, utilities, and the phone companies. The credit card industry the system standard is known as ANSI Standard X4.13-1983, and the system used is known as “IIN”.
Within that system, the individual issuers have their own unique way of using the system. An American Express credit card has a set of 15 numbers on its front. Those numbers are the card holder’s credit card account number with American Express. American Express account numbers are usually grouped into three subsets. The first subset has four numbers in it. The second subset has six numbers in it. The third and last subset has five numbers in it. In the Amex sequence of numbers in its 15-digit account number the 3rd and 4th numbers are for the type and currency. The account number itself is actually in the 5th through 11th numbers. The 12th, 13th, and 14th numbers are the card number within the account number for those individuals who do carry several of one issuer’s cards for various reasons. The last number, the 15th, carries check digit for the card. For American Express this 15 number sequence will begin with a prefix that has the numbers “34” or the numbers “37”. In the big wide world of the credit card industry, the different major, major credit card issuers each have a unique initial number for their own system credit card account numbers. American Express and Diner’s Club use the initial number “3” to identify their travel and entertainment credit cards. Visa uses the number “4”, MasterCard uses the number “5” and Discover Card uses the number “6”.
American Express has a security code like all other major credit cards. This code for Amex cards is called the “card identification code” or CID. Amex cards have the CID as a four-digit number that is printed on the front of the card. While the security strip on the back of the card has a goodly number of bits of information, the CID is not one of them. It is THE code that a card holder typically has access to only if the card holder is actually holding the said credit card. Other major cards use different names for their unique card ID codes; some use three numbers in their codes; some put their codes on the back of the card.
Some other interesting information, mainly about other major credit cards follows. The prefixes used by the other biggest of the major credit card issuers are as follows:
- Discover Card: 6011, 60112-60114, 601174, 601177-601179, 601186-601199, 622126-622925, 644-649, 65
- MasterCard: 51-55
- Visa: 4
For card number structure, here are two other examples:
- Visa uses two separate numbering schemes where the bank number is two through six, the account number is seven through 12 or seven through 15, and 13 or 16 is a check digit.
- MasterCard several schemes: depending on position two being a 1, 2, 3 or other, the bank number is position two and three, two through four, two through five or two through six. After the bank number up through digit 15 is the account number. The last number, 16, is a check digit.