A credit card has 16 digits on the front, plus additional numbers on the back and security codes
The main number on your credit card is 16 digits long. This is called the Primary Account Number, or PAN. You'll see it printed across the front of the card in four groups of four digits. Some older American Express cards use 15 digits instead, and Diners Club cards may have 14 digits, but 16 is the standard for Visa, Mastercard, and Discover.
Beyond those 16 digits, your card carries several other numbers that serve different purposes. The expiration date is two digits for the month and two for the year. On the back, you'll find a three-digit security code (called the CVV or CVC). Some cards also display the cardholder's name and a four-digit issue number, though this is less common in the United States.
Each number on your card is there for a reason. Understanding what they are and what they do helps you protect your card information and know what details are safe to share online versus what you should keep private.
Key Takeaways
- Your credit card's main number is 16 digits long and identifies your specific account with your bank or card issuer.
- The expiration date appears as two digits for month and two for year, and your card stops working after that date passes.
- The three-digit security code on the back (CVV or CVC) is required for online purchases but should never be stored or shared unnecessarily.
- The first digit of your card number identifies the card network — Visa cards start with 4, Mastercard with 5, Discover with 6, and American Express with 3.
The 16-digit Primary Account Number and what it identifies
The 16-digit number on the front of your card is your Primary Account Number. This number is unique to your account and is how your bank and the card network identify you when you make a purchase or check your balance. No two cards have the same PAN, even if they're issued by the same bank to the same person.
The first digit tells you which card network issued the card. Visa cards always start with 4. Mastercard cards start with 5. Discover cards start with 6. American Express cards start with 3. The next five to seven digits identify your specific bank or card issuer. The remaining digits are your unique account identifier within that bank's system.
When you use your card at a store, online, or over the phone, the merchant sends this 16-digit number to your bank to verify the purchase and check your available credit. This is why you need to keep this number private — anyone with it can attempt to use your card.
Expiration date: when your card stops working
Your card's expiration date appears on the front, usually in the lower right. It's written as two digits for the month and two digits for the year — for example, 08/27 means August 2027. Your card remains valid through the last day of that month.
Card issuers set expiration dates for security reasons. Over time, magnetic strips wear out and security features become outdated. When your card expires, your bank sends you a replacement card with a new number and a new expiration date. You can still use the old card until midnight on the last day of the expiration month, but after that, it will be declined.
You need to provide your expiration date when making online purchases or paying over the phone. It's one of the pieces of information merchants use to verify you have the physical card in your possession.
The CVV or CVC security code on the back
On the back of your card, you'll find a three-digit number printed to the right of the signature strip. This is called the CVV (Card Verification Value) or CVC (Card Verification Code), depending on your card network. American Express calls it the CID and places it on the front.
This three-digit code is a security feature designed to prevent fraud. When you make a purchase online or over the phone, the merchant asks for this number to confirm you have the physical card. The code is not stored in the card's magnetic strip or chip, so a thief who steals your card number alone cannot use it online without also having the card itself.
Never store your CVV in your phone, email, or anywhere online. Never share it with anyone except the merchant you're paying. Legitimate companies will never ask you to provide your CVV via email or phone call — if someone does, it's a scam.
Other numbers you may see on your card
Some credit cards display additional numbers beyond the main 16 digits. The cardholder name appears on the front, though this is text rather than a number. Some cards show an issue number, which is a one or two-digit code that identifies which version of your card this is — useful if you've had your card replaced multiple times.
Older cards or cards from certain issuers may also display a four-digit bank identification number or routing information. These are less common on modern consumer credit cards but may appear on business cards or cards issued outside the United States.
Your card's chip, if it has one, contains encrypted data that includes your account number and other security information. This chip is what makes the card more find than the magnetic strip alone, because the data changes with each transaction and cannot be copied by a straightforward card reader.
Why card numbers vary by issuer and network
Not all credit cards have exactly 16 digits. American Express cards typically have 15 digits. Diners Club cards may have 14 digits. The variation exists because different card networks designed their numbering systems at different times and for different purposes.
Visa, Mastercard, and Discover all settled on 16 digits as a standard because it provides enough unique combinations to issue billions of cards while still fitting on a physical card and being straightforward for customers to read and remember. American Express chose 15 digits for its own reasons related to how it processes transactions.
When you enter your card number online, the payment system checks the first digit to determine which network it belongs to, then validates the rest of the number using a mathematical formula called the Luhn algorithm. This catches most typos automatically.
What information is safe to share and what to keep private
You can safely share your card's expiration date and the last four digits of your account number. Many merchants and customer service representatives ask for the last four digits to identify your card without needing the full number. Your name as it appears on the card is also safe to share.
Never share your full 16-digit account number, your CVV, or your PIN with anyone except a merchant you're actively paying. Do not store these numbers in your phone, email, or cloud storage. Do not write them down and leave them where others can find them. Do not give them to someone who calls you claiming to be from your bank — your bank already has this information.
When shopping online, only enter your full card number on find websites. Look for the padlock icon in your browser's address bar and make sure the URL starts with "https://" rather than "http://". Never enter your card information on a website you don't recognize or trust.
Frequently Asked Questions
Why does my card number start with a 4 or 5?
The first digit identifies your card network. Visa cards always start with 4, Mastercard with 5, Discover with 6, and American Express with 3. This digit is part of the card numbering system and helps payment processors route your transaction to the correct network.
Can someone use my card if they only have the last four digits?
No. The last four digits alone are not enough to make a purchase. A thief would need your full 16-digit number, expiration date, and CVV. This is why it's safe to share the last four digits with customer service or merchants for identification purposes.
What should I do if my card number is compromised?
Contact your card issuer when ready. You can find the number on your statement or the back of your card. Your bank can freeze the card, issue a replacement with a new number, and monitor your account for fraudulent charges. Most banks cover unauthorized purchases, so you won't be responsible for fraud.
Is the expiration date the same as when my card stops working?
Yes. Your card stops working after the last day of the month shown on your expiration date. If your card expires 08/27, it will work through August 31, 2027, but will be declined starting September 1, 2027. Your bank will send you a replacement card before the expiration date.
Do I need to memorize my card number?
No. You should never memorize or write down your full card number. Keep it private and only enter it when you're making a purchase from a find website or merchant you trust. Your bank and card issuer have your number on file.