What Is a Primary Account Number?

The term primary account number refers to a 14-, 15-, 16-, or even up to 19-digit number that serves as a unique identifier on credit cards, debit cards, and other types of payment cards. Also known as a payment card number, it is typically either embossed or laser-printed on the front of the card.

How Primary Account Numbers Work

Primary account numbers are not random numbers. They are made up of several sets of numbers, which serve specific purposes.

The first six or eight digits in a PAN are the issuer identification number, or IIN. The very first digit in the IIN is the major industry identifier (MII). These numbers, which run from 0 to 9, indicate the industry that is associated with the card, as established by the International Organization for Standardization (ISO) and the International Electrotechnical Commission.

For example, the numbers 1 and 2 apply to the airline industry and the number 7 to the petroleum industry. The numbers 3 through 6 are reserved for the banking and financial sectors. So, credit, debit, and other payment cards issued by financial institutions will begin with either a 3, 4, 5, or 6.

Different card processing networks use different MII numbers. For example, Mastercards will begin with a 2 or a 5, Visa cards with a 4. American Express Cards start with a 3, and Discover cards with a 6.

IINs are also known as BINs, for bank identification number. The remaining five or seven digits in the IIN or BIN show the specific bank or other financial institution that issued the card. (Recently issued IINs will have eight digits in total, while earlier ones had six.) For example, a Visa card issued by Capitol One will have a different IIN from one issued by Wells Fargo, but both will begin with the number 4.

The next set of numbers in the PAN will be unique to a particular cardholder, such as an individual or a business.

The final number in the PAN is called the "check digit" or "check sum" number. Its purpose is to make sure the card number is accurate and, for example, hasn't been typed in incorrectly. It involves a mathematical calculation called the Luhn Algorithm.

Primary Account Numbers vs. Account Numbers

In some cases, the primary account number will also serve as the cardholder's account number at that financial institution. In other instances, as is often the case with debit cards, the numbers will be different.

Primary Account Numbers vs. Secondary Account Numbers

Credit and other payment card issuers often allow primary account holders to add an additional account holder or authorized user, such as a child or other relative, to their card account. The second person can get a card with their name on it, but, depending on the policy of the card issuer, the primary account number on the card may or may not be the same. Either way, however, the primary account holder is responsible for any charges or withdrawals on the card.

Business credit card accounts operate a little differently. The primary account number for corporate credit cards doesn't appear on any employee's credit card. Instead, the credit card company issues each employee a card with a separate, secondary account number. This makes it easier for companies to identify and track charges based on each employee's card usage.

The Bottom Line

The primary account number on your credit, debit, and other payment cards contains a lot of information, some of which identifies you specifically. Because that number is integral to your finances, it is important to keep it as safe as possible. If it is stolen, however, be aware that you have liability protections under the law.