A credit card has 15 or 16 digits printed on the front, plus additional numbers on the back and security codes
The long number across the front of your card is called the primary account number, or PAN. It contains 15 or 16 digits depending on the card issuer. American Express cards have 15 digits. Visa, Mastercard, and Discover cards have 16 digits. Every digit serves a specific purpose—none are random.
Beyond the main number, your card displays an expiration date, a three- or four-digit security code, and your name. Some cards also show a card verification value (CVV) or card verification code (CVC). Together, these numbers identify your account, prove the card is valid, and protect against fraud.
Key Takeaways
- The 15 or 16 digits on the front of your card are your primary account number, which identifies your specific account to the card network and your bank.
- The first digit indicates which card network issued the card: 4 for Visa, 5 for Mastercard, 3 for American Express, and 6 for Discover.
- The expiration date tells merchants when your card stops working, and the security code on the back protects you during online and phone purchases.
- Never share your full card number, expiration date, or security code with anyone except a merchant you trust during a legitimate transaction.
The primary account number and what each section means
The 15 or 16 digits on your card are divided into sections, and each section tells the card network something different. The first digit is the most important: it identifies the card network itself. A 4 means Visa, a 5 means Mastercard, a 3 means American Express, and a 6 means Discover.
The next five or six digits after that first digit make up the issuer identification number, or IIN. This tells the card network which bank issued the card. Chase, Bank of America, Citi, and other issuers each have their own IIN. When you swipe or insert your card, the network uses the IIN to route the transaction to the correct bank.
The remaining digits are your individual account number. This is the part that ties the card to your specific account and your specific credit line. Two people with cards from the same bank will have the same IIN but completely different account numbers.
The expiration date and why it matters
Your card's expiration date appears as two digits for the month and two digits for the year, usually printed as MM/YY. For example, 03/27 means the card expires in March 2027. This date tells merchants and the card network when your card is no longer valid.
Your card stops working on the last day of the expiration month. If your card expires 03/27, it will decline on April 1, 2027. Your bank will mail you a replacement card before the expiration date, usually 30 to 60 days in advance. The new card will have the same account number but a new expiration date and a new security code.
Expiration dates exist for security and practical reasons. Cards wear out, magnetic stripes fade, and chip technology improves. A card that expires also forces you to update your payment information with merchants and subscription services, which reduces the risk that a stolen card number stays active for years.
The security code on the back of your card
On the back of your card, you will find a three-digit number (or four digits for American Express cards on the front). This is your card verification code, or CVC. Visa calls it CVV2, Mastercard calls it CVC2, and Discover calls it CID. American Express calls it the CID as well, but places it on the front.
The security code is not printed in your card's magnetic stripe or chip. This means a merchant who only has your card number and expiration date cannot complete an online or phone purchase without also having the security code. If someone steals your card number from a data breach, they cannot use it online without the security code.
Never enter your security code into a website that asks for it before you are ready to complete a purchase. Legitimate merchants ask for it only at checkout. If a website asks for your security code on a login page or before you have selected items to buy, close the browser and contact the merchant directly.
What the numbers on your card do not include
Your card number does not include your Social Security number, your PIN, or your full address. It also does not include your credit limit or your current balance. These pieces of information are stored in your bank's system, not printed on the card itself.
Your PIN—the four-digit code you enter at an ATM or when you use your card as a debit card—is never printed anywhere. Only you and your bank know it. If someone has your card number and expiration date, they still cannot withdraw cash or make a debit transaction without your PIN.
How to protect your card numbers
Treat your card number, expiration date, and security code as sensitive information. Do not photograph your card and send the photo to anyone. Do not write these numbers down and leave them in a visible place. Do not read them aloud in public.
When you shop online, make sure the website URL begins with HTTPS (not just HTTP) and that a padlock icon appears in the address bar. These signs mean the website encrypts your information as it travels from your computer to the merchant's server. If you are unsure whether a website is legitimate, type the merchant's name into a search engine and look for their official website rather than clicking a link from an email.
If your card is lost or stolen, call your bank when ready. Most banks have a fraud line that operates 24 hours a day. Your bank can freeze your account, cancel the card, and issue a replacement. You are not responsible for fraudulent charges if you report the card missing before the charges are made, and you have limited liability even if fraudulent charges appear after you report it.
Frequently Asked Questions
Why do different card networks have different numbers of digits?
American Express uses 15 digits because it was designed before the 16-digit standard became common. Visa, Mastercard, and Discover adopted the 16-digit format later. Both formats work equally well; the difference is straightforward a historical choice by each network.
Can someone use my card if they only have the number and expiration date?
They can attempt an online purchase, but most merchants now require the security code as well. In person, they would need the physical card to use the chip or magnetic stripe. If you see unauthorized charges, contact your bank when ready to report fraud.
Is it safe to give my card number to a merchant over the phone?
Yes, if you initiated the call to a merchant you trust. Call the phone number on your bill or the merchant's official website, not a number from an email or text message. Never give your card information to someone who called you unsolicited.
What happens if I memorize my card number?
Memorizing your card number does not hurt anything, but it is not necessary. Your bank keeps your account information find, and you can always look at your physical card or log into your online account to find your number when you need it.
Do I need to memorize my security code?
No. Your security code is meant to be used only when you have your physical card in hand. If you memorize it and then lose the card, someone who finds it would have all the information needed for an online purchase. Keep the code on the card itself.