What Is a Bank Identification Number (BIN)?

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A bank identification number (BIN) is the opening string of digits on a payment card, six or eight digits under the current international standard, that identifies the institution that issued the card. The same number is formally called an issuer identification number (IIN). When a card is used, the BIN tells the merchant’s payment processor which card network to route the transaction through and which issuer must approve or decline it.

What Is a Bank Identification Number (BIN)?

Every credit card, debit card, charge card, prepaid card, gift card and electronic benefit card that runs on a card network has a BIN. The numbering system comes from standards developed by the American National Standards Institute (ANSI) and the International Organization for Standardization (ISO). Today it is governed by ISO/IEC 7812, which defines how card numbers are structured and how issuer ranges are assigned.

“Bank identification number” is the traditional industry term. “Issuer identification number” is the term the standard uses, because issuers include retailers, fuel companies and other non-bank institutions. In practice the two names refer to the same digits.

How a Bank Identification Number Works

A full card number, called the primary account number (PAN), has three parts:

1. The BIN/IIN: the leading six or eight digits, identifying the issuer.
2. The individual account identifier: the middle digits, assigned by the issuer to a specific cardholder account.
3. The check digit: the final digit, calculated with the Luhn algorithm. It catches most typing errors, such as a single wrong digit, before a transaction is sent.

Card numbers can run up to 19 digits, although 15 and 16 digits are the most familiar lengths. In 2017 ISO revised the standard to lengthen the IIN from six to eight digits, with a transition deadline of April 2022. The pool of six-digit ranges was being used up. Eight digits create far more issuer ranges without making card numbers longer, because the account identifier portion shrinks to compensate.

When you pay, the processor reads the BIN before anything else. That lookup tells the system which network (Visa, Mastercard, American Express, Discover and others) carries the transaction and which issuer receives the authorization request. The issuer then checks whether the card and account are valid and whether the available balance or credit line covers the charge, and it returns an approval or a decline.

Interpreting a Bank Identification Number

The first digit, the MII, places the card in a broad industry category:

Some network prefixes are widely known. Visa numbers begin with 4. Mastercard uses 51 to 55 and the 2221 to 2720 range. American Express begins with 34 or 37, and Discover includes ranges starting with 6011 and 65. Beyond the network, a BIN database maps each range to attributes such as:

• the issuing institution
• the card brand
• the card type (credit, debit, charge or prepaid)
• the product level (for example classic, platinum or corporate)
• the issuer’s country

These attributes come from the range assignment, not from the digits themselves, so a system has to look the range up.

Why Is a Bank Identification Number Important?

Routing and speed. The BIN lets one terminal or checkout page accept cards from many networks and issuers, because the processor can send each transaction to the right place within seconds.

Fraud screening. Merchants and processors compare BIN attributes with the details of a transaction. One example is a card issued in one country being used on a device or with a billing address in another. A mismatch is not proof of fraud, but it can trigger extra verification, such as an address check or a one-time passcode.

Acceptance rules. Because the BIN reveals card type, merchants can treat certain ranges differently. Some fuel pumps and online merchants restrict prepaid or foreign-issued ranges, and some merchants apply different processing for debit and credit cards. Checkout forms also use the leading digits to display the right card logo and to validate the expected number length.

Issuer management. Banks use separate BINs to keep product lines apart. That is why a single bank can have many BINs: its debit cards, consumer credit cards, business cards, co-branded cards and cards issued in different countries may each sit in their own ranges.

Example of a Bank Identification Number

Hypothetical example. A driver pays at a fuel pump with a card whose number begins 4123 4567 (an illustrative number, not a real issuer range).

• The leading 4 marks a banking and financial card and points the processor to the Visa network.
• The full eight-digit BIN, 41234567, matches a range that the processor’s BIN table records as, say, a U.S.-issued consumer debit card from a particular bank.
• The pump’s system confirms that it accepts that card type, then sends an authorization request through the network to that bank.
• The bank checks the account status and available funds and approves or declines.

If the range had been flagged as a type the station does not accept, the pump could reject the card before any request reached the bank.

Limitations of a Bank Identification Number

A BIN identifies an issuer range, not a person or an account. It cannot tell a merchant who the cardholder is, what the balance is or whether a particular card is stolen. Those answers come from the issuer during authorization.

BIN data also has blind spots:

• Ranges change. Banks merge, sell portfolios and reassign ranges. The move to eight-digit BINs means older tables keyed on six digits can misidentify cards.
• Tokens can mask the real BIN. When a card is loaded into a digital wallet, the device often transmits a network token with its own number instead of the actual card number, so merchant-side BIN checks may see the token range.
• The digits are not secret. Because a BIN is shared by many cards and is easy to look up, knowing it gives no proof that someone is genuinely connected to your bank.

That last point is the basis of BIN scams. A caller poses as your bank’s fraud department, recites the first digits of your card to seem legitimate, then asks you to “confirm” the remaining digits, the expiration date, the security code or a one-time passcode. A real bank does not need you to read your card back to it. Hang up, call the number on the back of your card and report the attempt. In the U.S. you can also file a complaint with the Federal Trade Commission.

BIN vs. Routing Number, BIC and Account Number

These identifiers are often confused because all of them point to a bank in some way:

A BIN is not a routing number. A debit card’s BIN and the routing number of the checking account behind it are unrelated numbers in separate systems. Nor is it a bank identifier code (BIC) under ISO 9362. A BIC registered on the SWIFT network is called a SWIFT code. Some sources use “BIN” loosely for “bank identifier,” but in card payments the term means the card prefix.

FAQs

The Bottom Line

Cardholders should know that the first digits of a card are shared by many cards and easy to look up, so a caller who recites them proves nothing. If someone claiming to be your bank asks you to confirm the rest of your card details, hang up and call the number on the back of the card. Merchants rely on BINs for routing and screening but still need the issuer to verify the account.