What Is an Issuer Identification Number (IIN)?

Search Fintrev

Search our guides, reviews and glossary.

An issuer identification number (IIN) is the opening sequence of digits on a payment card that identifies the institution that issued the card. When a card is used, the IIN tells the payment system which card network the card belongs to and which bank or other issuer holds the account, so the transaction can be routed to the right place for approval. IIN is the formal name in the international standard. Many people in banking still call the same digits the bank identification number (BIN).

How an Issuer Identification Number Works

Card numbers are usually 15 or 16 digits long, and the standard allows up to 19. Every PAN follows the same three-part layout:

1. Issuer identification number. The leading digits identify the issuer and, through the first digit, the industry.
2. Individual account identifier. The middle digits are assigned by the issuer to a specific card account.
3. Check digit. The last digit is calculated from all the others using the Luhn algorithm.

The IIN expanded from six to eight digits because the number of card issuers and card programs grew faster than six-digit ranges could accommodate. A longer IIN leaves fewer digits for individual accounts within each issuer range but allows many more issuer ranges. A 15- or 16-digit format still allows roughly one quadrillion (1,000,000,000,000,000) combinations, according to American Express.

Interpreting an Issuer Identification Number

Read an IIN from left to right. The first digit, the MII, places the card in a broad category:

• 1 and 2: airlines (Mastercard also uses a range beginning with 2)
• 3: travel and entertainment, as well as banking and financial
• 4 and 5: banking and financial
• 6: merchandising and banking/financial
• 7: petroleum (oil companies)
• 8: healthcare, telecommunications and other future industry use
• 9: assignment by national standards bodies

Because credit and debit cards sit in the banking and financial categories, they generally start with 3, 4, 5 or 6. The leading digit also signals the network: Visa cards begin with 4, Mastercard with 5 or 2, Discover with 6, and American Express with 3.

The digits after the MII narrow the card down to a particular issuer and often a particular card program. Two Visa cards from different banks both start with 4, but their following digits differ because each bank has its own IIN ranges. A large issuer can hold many ranges, for example separate ones for consumer credit, business and debit products.

IINs are not self-assigned. Under ISO/IEC 7812, published by the International Organization for Standardization and the International Electrotechnical Commission, a registration authority allocates them to qualifying institutions. The American Bankers Association has served as that registration authority. In practice, banks that issue on Visa or Mastercard typically receive their number ranges through the network.

Why Is an Issuer Identification Number Important?

The IIN is what makes near-instant card authorization possible. When you tap, insert or type a card number, the merchant’s payment processor reads the leading digits to determine which network should carry the request. The network then uses the IIN to send the request to the correct issuer, which checks the account and approves or declines the transaction.

Merchants and processors also use IIN data before a payment goes through. A checkout page can display the right card logo as soon as the first digits are entered. A processor can tell whether a card is credit, debit or prepaid, or whether it was issued in another country, and apply its own pricing or fraud rules accordingly.

Example of an Issuer Identification Number

Take a hypothetical card number, 4000 1234 5678 9017, which does not belong to any real issuer.

• 4 is the MII, placing the card in banking and financial, on a range used by Visa.
• 40001234, the first eight digits, would be the IIN identifying the issuer and card program.
• 5678901 is the individual account identifier.
• 7 is the check digit.

To confirm the check digit with the Luhn algorithm, start from the digit just left of the check digit and move left, doubling every second digit. If doubling produces a two-digit result, add its digits together (18 becomes 9).

• Doubled digits (1, 9, 7, 5, 3, 1, 0, 4) become 2, 9, 5, 1, 6, 2, 0, 8, which sum to 33.
• The remaining digits (0, 8, 6, 4, 2, 0, 0) sum to 20.
• 33 + 20 = 53. The check digit is whatever brings the total to the next multiple of 10, so it is 7.

Adding the 7 gives 60, which is divisible by 10, so the number passes. If someone mistyped one digit, say 5678 9117, the total would no longer end in zero and the form could reject it before any request reached the bank.

Limitations of an Issuer Identification Number

• It does not identify the cardholder. The IIN points to an issuer and product, not a person or an account balance.
• It does not prove a card is real or active. The Luhn check only catches typing errors and some transposed digits. A number can pass it and still be closed, expired or never issued. Only the issuer’s authorization response confirms the account.
• Lookup tables can be outdated. IIN ranges get reassigned when banks merge, sell portfolios or launch new programs, and the switch to eight-digit IINs means old six-digit lists may misidentify newer cards.
• Six digits may not be enough. Since multiple issuers can now share the same first six digits, identifying a debit card network by its first six digits still works, but identifying the specific issuer reliably may require all eight.

How the IIN Differs From Related Numbers

IIN vs. BIN. These describe the same digits. “Bank identification number” is the older industry term; IIN is the standard’s name, reflecting that issuers include non-banks.

IIN vs. card number. The IIN is only the first part of the card number (the PAN). The full number adds the account identifier and check digit.

IIN vs. CVV. The card verification value is a separate three- or four-digit code printed on the front or back of the card, depending on the issuer. It is not part of the card number. Its purpose is to show that the person paying likely has the physical card, since someone who stole only the number would not have the code.

IIN vs. virtual or tokenized numbers. A virtual card number is a different number linked to the same account, often used for online purchases so the main card number is not exposed. Phone-based payments in a digital wallet work on a similar principle, substituting a token for the real PAN.

The Bottom Line

Merchants, processors and anyone building a checkout rely on IIN data to route payments, show card logos and apply pricing or fraud rules. Because ranges get reassigned and the IIN now runs eight digits, older six-digit lookup tables can misidentify newer cards, so identifying a specific issuer reliably may require all eight digits. The IIN reveals the issuer and product, never the cardholder or the account balance.