What Is an Issuer Identification Number (IIN)?

Issuer Identification Numbers Explained in Less Than 3 Minutes

A customer makes a payment with a credit card.
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An IIN (issuer identification number) is the first six or eight digits of a payment card number that identify the card’s issuer. The number is critical for card payments because it identifies important information that merchant banks need to know to process transactions.

Learn what an issuer identification number is and why it’s used.

Definition and Example of an Issuer Identification Number

An IIN is the first six or eight digits at the beginning of a payment card number that identify the issuer of the card.

  • Alternate name: Bank identification number (BIN)
  • Acronym: IIN

For example, let’s say your credit card number is 5412 7512 3412 3456. If your issuer uses a six-digit IIN, then the digits 541 275 make up the IIN on your card. If your issuer uses an eight-digit IIN, then your IIN is 5412 7512.

How Issuer Identification Numbers Work

Every time a payment card is used, the merchant’s bank needs to know which bank issued the customer’s card in order to route, clear, and settle the transaction. It uses these identification numbers—the IIN—since it can’t physically see the issuer’s logo on the card.

The first digit in an IIN signifies the major industry identifier (MII). In a credit card context, the MII typically signifies the credit card network.

First Digit of IIN Industry/Credit Card Company
1 Airlines
2 Mastercard
3 Entertainment and travel (includes Diners Club and American Express)
4 Visa
5 Mastercard
6 Discover
7-9 Petroleum, health care, and other industries

This means that every credit card that begins with the number “5” is a Mastercard, and every card that begins with a "4" is a Visa card.

The digits in the IIN following the first digit signify the credit card issuer, such as a bank or other financial institution. These numbers are known as bank identification numbers (BINs). If your card number began with the IIN 370 277, it would indicate that it was an American Express card issued by Wells Fargo.

IIN guidelines are set by the International Standards Organization (ISO) in its ISO/IEC DIS 7812 standard. These are standardized worldwide, so an IIN can reliably identify the issuer behind a particular card.

The ISO is also responsible for a variety of other international standards, including country codes, film speed, date and time format, and currency codes.

For efficient distribution, the ISO first assigns blocks of IINs to an administrative blockholder or a card scheme blockholder. These institutions act as intermediaries between the ISO and card issuers, and will issue INNs to credit-card issuers

While all IINs used to be made up of six digits, the ISO expanded them to eight digits in 2017. Existing issuers with a six-digit IIN were given access to 100 eight-digit IINs based on their original six-digit codes.

Of course, just because the ISO made this change to the IIN standard doesn’t mean it had immediate effect. Mastercard and VISA will only begin assigning eight-digit IINs beginning in April 2022.

Issuer Identification Number vs. Primary Account Number

Payment card numbers are made of more than just the IIN. The last eight to 19 digits of a card are the primary account number (PAN). While the IIN is associated with the card issuer, the PAN is associated with the individual cardholder.

Issuer Identification Number (IIN) Primary Account Number (PAN)
Six or eight digits Eight to 19 digits
Standard changed to eight digits in 2017 Standard changed to 10 to 19 digits in 2017
Identifies the card issuer Identifies the cardholder

In the same standard that updated the length of IINs to eight digits, the ISO also established the minimum length for PANs at 10 digits instead of eight in 2017. The ISO implemented these changes to accommodate a growing number of credit-issuers that would eventually use all available IINs under the previous number scheme.

Key Takeaways

  • An IIN is the first six or eight digits on a payment card. The first digit in an IIN indicates the card network, and the remaining digits in the IIN indicate the card issuer.
  • IINs on payment cards help the merchant’s bank efficiently route and process a given transaction.
  • The IIN is followed by the PAN on a card. While the IIN identifies the card issuer, the PAN is specific to the cardholder.