What The Numbers On Your Credit Card Mean

The string of numbers on you credit card houses a batch of information. For instance, the first number tells you what kind of card it is — 4 for Visa, 5 for MasterCard, and so on. Visa cards are always 16 digits long and have other identifying characteristics:

When looking at the balance of the numbers, the 2nd through 6th digits are the bank number, and the 7th-15th numbers are your account number. The remaining digit is known as the "check digit," which is used to help determine whether or not the overall number is legitimate.

[Five Cent Nickel]


    I dont like when, buying something over the phone or online, youre asked for the three digit code on the back of the card.
    That code is suppose to remain with the card holder and not given out.
    That code, in case of a fraudulent transaction, is used to prove if youre the true card holder or not. If you dont know the code then you dont have the card.

    When a site or someone asks for that code you are giving then the cards security code.
    That code is not required for the transaction. It should not be asked for and should not be given.
    Very dodgy!

      Those CVV (3-digit code) comments are not correct, I'm sorry. The primary purpose of the code is *exactly* that situation - an additional security check for phone or online transactions to verify the card is present.

      Depending on the Merchant Agreement, you are often *required* to obtain the CVV - my ANZ (and previously NAB) EFTPOS terminals specifically prompt for it to be entered for phone and online transactions.

      Not dodgy - the actual terminal requests it.

      Of course, giving details to a dodgy vendor is a different issue.

      See wikipedia and elsewhere for more information.


    Actually, credit card numbers have a unique algorithm to see if they are valid or not. Off memory its like certain numbers (or every second) numbers must add up to 10 and be divisible by 2. I can't remember the exact details.

    A quick Google retrieves that credit cards use the Luhn Algorithm http://en.wikipedia.org/wiki/Luhn_algorithm

    Here is an extract:

    " 1. Double every second digit, from the rightmost: (1×2) = 2, (8×2) = 16, (3×2) = 6, (2×2) = 4, (9×2) = 18
    2. Sum all the individual digits (digits in parentheses are the products from Step 1): 6 + (2) + 7 + (1+6) + 9 + (6) + 7 + (4) + 9 + (1+8) + 4 = 70
    3. Take the sum modulo 10: 70 mod 10 = 0; the account number is valid.

    And, deal with enough credit card numbers, and you'll begin to recognise the patterns without even having to wait for the customer.

    eg '4564 6090' is a very common one.

    Also, Amex is 15 digits and starts with 37 - anything which is 3760.. is usually an actual Amex card while something like 3778 is a joint bank/Amex card (such as an altitude card from Westpac).

    Diners is always 14 digits also starting with 3.

    The things you pick up working hotel reservations.

    warcroft - try buying a pizza over the phone without giving them your 3 digit security # and you'll go very hungry my friend!

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