Broken Secrets

The Meaning of the Digits on Your Credit Card

February 7, 2011 at 2:00 am Chad Upton 12 comments

By Chad Upton | Editor

There are thousands of different credit cards from the major issuers, but all of them have one thing in common: the meaning of the numbers on the card.

Most major cards have 16 digits on them and each number has a specific meaning.

Digit 1 (Industry ID)

• 1 and 2 are Airline cards
• 3 – Travel and Entertainment
  • ex. Amex
• 4, 5 – Banking and Financial
  • ex. Visa, Mastercard
• 6 – Merchandising and Banking
  • ex. Discover, Diners Club
• 7 – Petroleum
• 8 – Telecom
• 9 – Misc.

Digits 2-6 (Issuer ID)

Although all Visa cards start with the number 4, the following 5 digits indicate which bank that issued the Visa card. Mastercards start with 5, Discover starts with 6. You’ll notice that some websites don’t ask you what type of card you have — they obviously know what the digits on the card mean.

Digits 7-15 (Account ID)

The unique number that identifies your account.

Digit 16 (Checksum)

This single digit is one of the most important ones on the card. Much like the last digit of a barcode, the sole purpose of this digit is to allow validation of the rest of the number. In other words, there is a mathematical relationship between the numbers on the card, so if the number is entered incorrectly, the card validator system can indicate the card number was entered incorrectly.

You can validate a card number on your own too. Double every other number, starting with the first number. Add the result of those multiplications to all of the other digits on the card, treating all numbers as individual digits, including double digit results from the doubling operation. If the sum of all these numbers is divisible by ten, the number is valid according to the ISO standard. However, a valid card number doesn’t necessarily mean the number is an active account or that charges can be made with it.

In the early days of credit cards, they didn’t actually check this before imprinting a card for small purchases and larger purchases were verified with a phone call. Today, it’s usually done electronically. When your card is swiped, the number is validated by the point of sale system (using the method above) and if the card number is valid then an electronic request is sent to verify the charge will be accepted by the card issuer.

Some retail stores will ask to see your card so they can manually type in the last four digits on the card. This verifies that the number embossed in the card is the same number that is programmed to the magnet stripe on the back; this is one way retailers can catch counterfeit or reprogrammed cards before the goods leave the store.

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Sources: Abby’s Guide, HowStuffWorks, Merriam Park, Mint

Entry filed under: Money. Tags: american express, amex, cc, credit card, mastercard, money, visa.