The first four digits identify your card's issuer and network

The first four digits of your credit card are called the Issuer Identification Number, or IIN. They tell you which bank or financial company issued the card and which payment network it runs on — Visa, Mastercard, American Express, or Discover. This number is standardized across the industry, so the pattern is the same whether you're looking at a card from your local bank or a major national lender.

These digits matter because they determine where transactions are routed, which merchants accept your card, and sometimes what protections or rewards come with it. When you're troubleshooting a declined transaction or trying to remember which card is which, the IIN gives you a quick answer without having to read the full card number or call customer service.

Key Takeaways

  • Visa cards start with 4, Mastercard with 5, American Express with 3, and Discover with 6.
  • The first four digits are the Issuer Identification Number and identify both the payment network and the bank that issued your card.
  • Knowing your card's IIN helps you troubleshoot declined transactions and understand which merchants might not accept your card.
  • The remaining digits on your card encode your account number and a security check, but the first four are the only ones that identify the issuer.

Visa cards always start with 4

Any Visa card begins with the digit 4. The second, third, and fourth digits vary depending on which bank issued the card, but that first 4 is consistent across every Visa in circulation. This makes Visa straightforward to spot at a glance.

Visa is the largest payment network in the world, so you'll encounter this pattern on cards from thousands of different banks and credit unions. The second through fourth digits help Visa and the issuing bank route the transaction correctly, but they don't tell you anything about the card's features or rewards — that information comes from the bank itself, not the network.

Mastercard cards start with 5

Mastercard cards begin with 5. Like Visa, the digits that follow identify the specific issuing bank, but the 5 is the universal marker for the Mastercard network.

Mastercard is the second-largest payment network globally. It's accepted almost everywhere Visa is accepted, and the two networks have very similar fraud protections and dispute processes. The main differences between a Visa and a Mastercard come from the bank that issued it, not from the network itself — so a rewards Mastercard from one bank might offer very different benefits than a basic Mastercard from another.

American Express cards start with 3

American Express cards begin with 3, followed by either a 4 or a 7 in the second position. So you'll see either 34 or 37 as the first two digits. American Express is both a payment network and an issuer — they issue their own cards rather than licensing their network to banks the way Visa and Mastercard do.

American Express cards are less widely accepted than Visa or Mastercard, particularly at smaller merchants or international locations. However, they often come with premium benefits like travel insurance, concierge services, and higher rewards rates. The trade-off is that not every merchant takes them, so it's worth checking before you rely on an American Express card as your only payment method.

Discover cards start with 6

Discover cards begin with 6. Like American Express, Discover is both a payment network and an issuer, meaning Discover issues its own cards rather than licensing its network to banks.

Discover has smaller market share than Visa or Mastercard, so it's accepted at fewer merchants overall. However, Discover cards often come with strong cash-back rewards and no annual fees. Many people carry a Discover card alongside a Visa or Mastercard to take advantage of the rewards while ensuring they have a widely accepted card for situations where Discover isn't taken.

What the remaining digits tell you

After the first four digits, the rest of your card number encodes your account number — the specific account at your bank that the card is tied to. The very last digit is a check digit, a mathematical verification that the entire number is valid. This check digit is calculated using the Luhn algorithm, a formula that catches most typos or misread numbers.

The account number and check digit don't tell you anything about the card's features, rewards, or issuer beyond what the first four digits already told you. If you need to know whether your card has travel insurance or a specific rewards rate, you'll need to check your card agreement or call the bank — the card number itself won't tell you that.

Why this matters when your card is declined

If a merchant's system rejects your card, knowing the IIN can help you figure out why. Some smaller merchants or international retailers don't accept American Express or Discover, even though they accept Visa and Mastercard. If your Amex or Discover card is declined, try a Visa or Mastercard if you have one — the problem may be the network, not your account.

Conversely, if a Visa or Mastercard is declined, the issue is usually with your account or the transaction itself, not the network. In that case, call your bank to find out whether there's a fraud hold, insufficient funds, or an address mismatch with the merchant's system.

Frequently Asked Questions

Can I tell what bank issued my card just from the first four digits?

The first four digits tell you the network and narrow down the issuer, but you can't identify the exact bank from those digits alone. Different banks issue cards on the same network with the same first four digits. You can find out which bank issued your card by calling the number on the back of the card or checking your account online.

Do debit cards follow the same pattern as credit cards?

Yes. Debit cards issued by Visa or Mastercard follow the same IIN pattern as credit cards — Visa debit cards start with 4, Mastercard debit cards start with 5. The first four digits tell you the network, not whether the card is a credit or debit card. You'll need to check your account or card agreement to know which type you have.

What if my card starts with a different number?

Most cards in circulation start with 3, 4, 5, or 6. If your card starts with a different digit, it may be a specialty card like a Diners Club card (starts with 3), a JCB card (starts with 3), or a regional network card. These networks are less common in the United States but are used in other countries or for specific purposes.

Does the IIN change if I get a replacement card?

Usually not. If your bank sends you a replacement card because yours was lost or damaged, the new card will typically have the same first four digits and account number as the old one. The only exception is if you switch to a different card product entirely — for example, upgrading from a basic Visa to a premium Visa rewards card from the same bank.