What is a credit card number?

Updated:Apr 17, 2026

5 min read

Your credit card number is the long string of digits on your card, usually 16 in total. It's formally known as a Primary Account Number, or PAN. It's used to identify your card when you make purchases online or over the phone, and it's unique to your card.

What do the digits in a credit card number mean?

The digits follow a specific structure. Each part of the number has a different purpose.

The Issuer Identification Number (IIN)

The first six to eight digits are called the Issuer Identification Number, or IIN. Sometimes you'll see this called a Bank Identification Number (BIN). This is standardised globally under the ISO/IEC 7812 international numbering standard.

The very first digit is known as the Major Industry Identifier (MII). It identifies the industry sector the card issuer operates in: 4 and 5 are banking and financial, while 3 is travel and entertainment.

The specific ranges below then identify the network.

4 = Visa
51 to 55 or 2221 to 2720 = Mastercard
34 or 37 = American Express

So if your card number starts with a 4, it's a Visa card. If it starts with a number between 51 and 55, or between 2221 and 2720, it's a Mastercard. 34 or 37 is American Express.

The remaining digits of the IIN identify the specific bank or institution that issued the card.

The individual account number

The digits after the IIN, up to the second-to-last digit, form your individual account number. This is the unique sequence that ties the card to your specific account with your card issuer.

The check digit

The final digit is a validation number. It's calculated using a mathematical formula called the Luhn algorithm. When you type your card number into an online payment form, the site can run this calculation before even contacting your bank. If you accidentally transpose two digits, the check digit won't match and you'll be prompted to re-enter the number straight away.

How long is a credit card number?

Most credit card numbers (including Zable) are 16 digits long, displayed as four groups of four. American Express uses 15 digits. Some cards use different lengths depending on the issuer, though 16 is by far the standard for UK credit cards.

What are the other numbers on a credit card?

Your card number is one of several numbers on your card. Here's what the others are for.

Expiry date

Printed in MM/YY format on the front of your card. You'll need it alongside your card number for online purchases. Your issuer will send a replacement card before this date.

Security code (CVV)

The three-digit number on the back of your card. American Express places a four-digit version on the front. It's used to verify card-not-present purchases, such as online or phone payments. For a full explanation of how it works, see our guide on what a CVV is and how it protects you.

Issue number

Some older UK credit cards include an issue number. This is a short sequential number that increments each time the card is replaced: your first card would show 1, a replacement after loss would show 2. Most modern cards no longer include one. If an online form asks for an issue number and your card doesn't have one, you can usually leave the field blank.

Does my credit card number change?

Yes, in certain situations. Your card issuer will issue a new card with a different number if the card is lost or stolen, if the card expires and is renewed, or if suspicious activity is detected on the account.

Your underlying credit account continues as normal. However, any recurring payments or subscriptions linked to your old card number will need to be updated with the new one.

Is a credit card number the same as a bank account number?

No. A credit card number (PAN) is unique to the card itself, not to a bank account. It doesn't work in the same way as a sort code and account number, which identify a current account held with a bank. Credit cards don't have sort codes.

If you need to pay your credit card balance by bank transfer, your issuer will provide a separate sort code and account number specifically for that purpose. These are not printed on your card.

For more on how the two types of card differ, see our guide on the difference between a credit card and a debit card.

What is a virtual credit card number?

A virtual credit card number is a temporary alternative number linked to your actual card account. You can use it for online purchases in place of your real card number. If the virtual number is compromised in a data breach, your actual card details remain protected. Some card issuers offer virtual card numbers as a feature.

How do I keep my credit card number safe?

A few straightforward habits help protect your details:

Only enter your card number on sites you trust, and look for HTTPS in the address bar before paying
Never share your card number by email or over the phone unless you made the contact and trust who you're speaking to
Check your receipts: under PCI DSS payment security standards, merchants are required to mask part of your card number.

If you suspect your card details have been compromised, contact your issuer immediately to cancel the card. For further guidance on staying safe, see our fraud awareness guide.

FAQs

Do credit cards have sort codes?

No. Sort codes identify current accounts held with banks and are not part of how credit cards work. If you're making a bank transfer to pay your credit card balance, your issuer will give you a specific sort code and account number to use for that purpose.

What is the issue number on a credit card?

An issue number is a short sequential number found on some older UK credit cards that increments each time the card is replaced. Most modern cards no longer include one. If an online form asks for it and your card doesn't have one, leaving the field blank will usually work.

How many digits is a credit card number?

Most credit card numbers are 16 digits. American Express uses 15 digits. Some cards use different lengths depending on the issuer, though 16 is standard for the vast majority of UK credit cards.

What does the first digit of a credit card number tell you?

The first digit is known as the Major Industry Identifier (MII) and identifies the industry sector the issuer operates in. The specific range of opening digits then identifies the network: 4 for Visa, 51-55 or 2221-2720 for Mastercard, and 34 or 37 for American Express.

Can someone use my credit card number without the physical card?

For online or phone purchases, a fraudster would also need your expiry date and CVV as well as your card number. For in-person chip and PIN transactions, the physical card is required. This is why protecting all three details together matters, and why receipts only display a masked version of your number.

This blog is for informational purposes only and does not constitute financial advice. Please speak to a qualified financial adviser before making financial decisions.

Credit cards