Issuer Identification Numbers (IIN)

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Issuer Identification Numbers (IIN)

Key takeaways
* An Issuer Identification Number (IIN), also called a Bank Identification Number (BIN), is the leading group of digits on a payment card that identifies the issuing financial institution and the card network.
* IINs are part of the Primary Account Number (PAN); the PAN includes the IIN, the cardholder’s account digits, and a final check digit.
* The first digit is the Major Industry Identifier (MII), and card numbers are validated using the Luhn algorithm.
* IINs typically contain eight or nine digits (earlier systems used six); PANs can be up to 19 digits long.

What is an IIN?

An Issuer Identification Number (IIN) is the initial sequence of digits on a credit, debit, or other payment card that identifies the card-issuing bank or institution and the payment network it belongs to. Merchants, processors, and networks use the IIN to route transactions and verify the card’s origin.

Structure and standards

  • The IIN is defined under the ISO/IEC 7812 standard.
  • The very first digit of the PAN is the Major Industry Identifier (MII), which indicates the sector:
  • 1–2: Airlines
  • 3–6: Travel and banking/financial services (cards generally start with 3, 4, 5, or 6)
  • 7: Petroleum/oil
  • (Other MIIs cover additional industries.)
  • Common network prefixes:
  • Visa — begins with 4
  • Mastercard — begins with 2 or 5
  • Discover — begins with 6
  • American Express — begins with 3
  • Modern IINs are usually eight digits for international use (nine digits may indicate closed/national ranges). After the IIN come the account identifier digits and a single check digit.

Primary Account Number (PAN) and validation

  • The PAN is the full card number: IIN + account number + check digit.
  • The final digit is a check digit used with the Luhn algorithm to validate the card number and help detect input errors.

Why IINs matter

  • They let merchants and processors instantly determine the issuing bank and appropriate routing for authorization.
  • IINs help in fraud prevention, transaction routing, analytics, and card-product identification (e.g., distinguishing rewards or business cards).

Related card details and consumer protections

  • IIN vs. account number: Your printed card number (PAN) can change if you get a replacement card, while the underlying account number with the financial institution may remain the same.
  • CVV (card verification value): A 3- or 4-digit code printed on the card that provides an extra layer of security for card-not-present transactions.
  • Virtual card numbers: Also called single-use cards, these are temporary PANs linked to your account used to reduce exposure of your primary card number in online transactions.
  • Authorized users: Card issuers may give authorized users a separate physical card number or the same number, depending on issuer policy. The primary account holder remains responsible for charges.
  • Receipt truncation (U.S. FACTA rule): Merchants printing electronic receipts must truncate card numbers, showing no more than the last five digits, and must not print the card expiration date.

Quick fact

A typical 15- or 16-digit card number allows for about 1 quadrillion (1,000,000,000,000,000) possible combinations.

Bottom line

The IIN is the part of a payment card number that identifies the issuing institution and card network. Together with the account digits and the check digit, it forms the PAN used to route and validate transactions securely and efficiently.