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What The Numbers On Your Credit Cards Mean

by SharonKurheg

Some people collect their frequent flyer miles and hotel points the old-fashioned way – with multiple flights and lots of hotel stays. For example, if you’re a business traveler, that could sustain the number of points and miles you might want for travel.

But suppose your travel is usually limited to leisure trips. In that case, you probably use travel and miles rewards credit cards to build up the number of points, miles and maybe even free night certificates you have (if you’re just getting started in collecting points and miles, here’s a good primer on how to get started).

Regardless of what kind you have credit cards, of course, they all have their similarities. They’re all the same size. They’re all plastic (Well, except for the ones that are metal. We still don’t “get” those, and man, trying to get rid of them is a pain. But we did find out how to do it.). They all have some information about what bank they’re from, the type of card they are, and they usually have some sort of picture or decoration on them, although they could be as fancy or as plain as could be.

And, of course, all credit cards have numbers on them.

Most credit cards have 16 digits – 4 groups of 4 numbers. American Express cards have 15 digits, laid out in groups of 4, 6 and 5.

The numbers appear to be just random, but there’s a pattern that they follow. Here’s what they all mean:

The 1st number

The first number on your credit card is called the Major Industry Identifier (MII). It reveals what type of company the card is affiliated with (read: airline, gasoline company, etc.). They are:

1 – Airline
2 – Some Mastercard accounts since 2017
3 – American Express and Diners Club
4 – Visa
5 – Mastercard
6 – Discover
7 – Petroleum
8 – Telecommunications
9 – Government

The 2nd through 6th numbers

These five numbers, used in conjunction with the MII, are called the Issuer Identification Number (IIN) or Bank Identification Number (BIN). That number specifies which financial institution issued your card (Chase, Amex, Bank of America, Discover, Wells Fargo, Barclays, etc.). Each bank can have more than one identifying number (Wikipedia lists which banks use which numbers).

Have you heard? In April 2022, IINs/BINs are switching from 6 digits to 8. They’re doing this to increase the number of potential INNs/BINs so there won’t eventually be a shortage of them.

The rest of the numbers

All the other numbers (except for the last one – I’ll get to that in a second) is your account number. It’s unique to your specific credit card account.

The very last number

The last number on your credit card is called the check digit or the validator.  It’s a way to ensure that you’re giving the correct number, especially when providing your card information online or on the phone.

This is done by a special mathematical code that, of course, a computer can figure out in a split second, while we’d still be sitting there with a calculator. But, for a 16-digit card, for example, it’s:

  1. Double every other number (starting with the first)
  2. Separate any double-digit numbers that result into the sum of their parts (e.g., 14 becomes 1 and 4)
  3. Calculate the sum of the resulting numbers
  4. Calculate the sum of the numbers that were not doubled (i.e., the odd digits in the card number)
  5. Add the result of step c to the result of step d
  6. Divide by 10

(It’s the same thing for a 15-digit card, but start by doubling the second number rather than the first one).

Either way, if the result ends in 0, then the card number is correct. If the result is any other number, you typed it wrong (say, switched 2 of the digits in your card number), or whoever you gave the number to didn’t type it correctly. It’s a form of quality control to ensure that you get billed for what you’re purchasing.

Other stuff:

What about security codes?

The 15 or 16 numbers on your credit card allow proper payment. But the 3-digit (for Visa, Mastercard and Discover) or 4-digit (for Amex) card verification value (CVV) is a way to help prevent fraud.

When you pay online or via phone, that code helps ensure that you’re in possession of the said card, and it’s not a stolen number (when there are data breaches, thieves usually have the card numbers but not the CVVs).

Of course, CVVs don’t make everything foolproof – nothing says the person you give the CVV to isn’t nefarious and is writing down credit card numbers and respective CVV codes as they go along. But in general, it can be another step to prevent credit card fraud.

Magnetic strips vs. chip & PIN

All the info above, along with the card’s expiration date, is stored in that magnetic stripe on your credit card. Unfortunately, it’s relatively easy to extract all that info when you swipe your card. That’s why the U.S. is finally (*cough* albeit kicking and screaming *cough*) switching over to chip & PIN technology (of course, this is while the rest of the world is already continuing to contactless payments; and we are, too…just…SSLLOOWWLLYY).

Feature Photo: Pixabay

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This post first appeared on Your Mileage May Vary

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