Understanding Credit Card Numbers
Everyone is aware of the numbers embossed in gold or silver lettering across the middle of their credit cards. But did you know that these numbers are not just a random sequence — they actually have meaning. This part of the guide will take you through precisely what these numbers mean. Indeed, credit card numbers are a special case of ISO 7812 numbers (which is the international standard governing magnetic-stripe identification cards, of which credit cards are one type).
Generally, the ISO 7812 standard defines the numbers within its class to be of the following type: a single-digit major industry identifier (MII), a six-digit issuer identifier number (IIN), an account number, and a single digit checksum. In terms of credit card numbers the major industry identifier is considered to be part of the issuer identifier number and need not be a single figure. This is sometimes called the card Prefix.
Credit Card Prefix
The credit card number's prefix is a sequence of digits at the beginning of the main card number that determine the specific credit card network to which that number (and hence the card itself) belongs. Of these, the first six numbers of a credit card are known as the Bank Identification Number (BIN) and identify the institution that actually issued the card to the credit card holder. The remainder of the numbers are allocated by the issuer itself and the length of the number varies by issuer and card type, as below:
| Card Type | Prefix(es) | Length |
|---|---|---|
| American Express | 34 and 37 | 15 |
| Bankcard | 560–561 | 16 |
| Diners Club | 300–305, 36 and 38 | 14 |
| Discover Card | 6011 and 650 | 16 |
| JCB | 3 | 16 |
| JCB | 1800 and 2131 | 15 |
| MasterCard | 51–55, 36 | 14 or 16 |
| Visa | 4 | 13 or 16 |
Some card issuers employ the final digit of the card number as a checksum digit and only issue those card numbers that will pass a checksum test (where a calculation is mad on the sum of all the card's numbers that should result in the value of the checksum number). This prevents casual attempts at card fraud as only one number in ten will be vaild if the numbers are chosen at random. It also allows mistakes to be caught quickly if a card number is entered manually into a machine.
In most cases, the next group after the opening series of numbers represents the routing number of the card-issuing bank, the group after that is the user's account number, and the final digit is the checksum digit (as described above).
Cash-back Credit cards
This type of card is a relatively recent arrival in the marketplace. These cards generally offer reimbursement of a percentage of each purchase made (which can be as high as 1%). This type of card was pioneered by Sears which still offers discounts on purchases made in their stores. A popular variant of this cards allows the user to accumulate points on purchases or transactions from a number of vendors which can be used against purchases in a supermarket or store. Because of the incentives offered this type of card may well be worth investigating further if you're considering a credit card.
Credit Cards for Bad Credit
Despite what most people think, it is still possible to gain a credit card even if you have bad credit. However, these cards will come with a number of restrictions attached to them; restrictions not normally associated with normal credit cards. In addition, the credit limit will be much lower and the interest rate levied will be far higher. You may even have to take out a secured card which means that the loans taken out on the credit card need to be secured against a savings, deposited shares, a house or some other form of equity. Normally, once you have established that you will be responsible many of the restrictions imposed on these types of card will be lifted.
Ameircan Express
American Express has a very specific formula for its numbers where the first four numbers stand for country code, currency code and card type (charge or credit) the next two digits represent the card level (standard, gold, platinum) the next digit represents the billing cycle, the next four numbers stand for the account number. The number fourth from last represents the card's issue number (this starts at 1 and increases if the card is replaced because it was lost or stolen). The next two digits represent the number of the card issued to a given account. If there are two cards isued to an account then these would be 00 and 01, respectively. The final number represents the checksum digit.
Visa
The first digit is a 4 and represents the Visa card network. Digits two through six represent the number of the issuing bank. The remaining numbers (from seven to the penultimate number) are the account number and the final number is, once again, the checksum digit.
MasterCard
The MasterCard network is identified by the first two numbers on the card (which is either 36 or lies in the sequence 51—55). The number of the issuing bank is repesented by a sequence of numbers from the third digit to anywhere between the fourth and sixth digits. The remaining numbers (apart from the very last) represent the account number. Again, the final digit is the checksum number.
Other Credit Card Codes
As well as the main credit card number the card also bears a number of other number codes, which include issue and expiry dates (to the nearest month) as well as issue codes and security codes. These numbers may be used in conjunction with the main number to identify how genuine the card is. The main code used for this purpose is the security code which is generally the last thee numbers printed on the signature strip at the back of the card. However, in the case of American Express cards this is often a four-digit number printed on the front of the card.