Who Assigns Bank ID & Routing Numbers?

Definition of a Bank Identification Number

A bank identification number, sometimes called an issuer identification number, is a credit card number's first four to six digits. A bank identification number can also be found on charge cards, debit cards and electronic benefit cards. The series of numbers is printed on the card, on statements and in online transactions to identify which bank or organization issued the card. The number can also be used to detect theft, by comparing the issuer to the cardholder's address.

To ensure that no two organizations have the same bank identification numbers, the American Bankers Association issues card numbers in the United states. The bank identification number identifies the organization that issues the cards in question; it may not necessarily be a traditional bank. For example, Diner's Club International cards can be identified by the first six digits on the card. Greendot prepaid Mastercards have the prefix 519285, while Maestro debit cards have the bank identification number 560251 or 581353.

The ABA routing number, sometimes called a check routing number or routing transit number, is a nine-digit number assigned to banks and other financial institutions by the American Bankers Association. The number identifies the particular institution a check or electronic check was drawn on. The routing number can be found at the bottom of a check with the account number and check number. The routing number can also be found on paper checks at the top right in fractional form for hand processing of checks.

The American Bankers Association assigns routing numbers to financial institutions. The number was developed by the ABA in 1910 to ensure that negotiable instruments could be easily routed to their originating institution. The ABA routing number was originally assigned to check processing endpoints but now encompasses online banking institutions, electronic funds transfers and automated clearinghouses. ABA routing numbers are only issued to financial institutions that have an account with the Federal Reserve Bank.