A bank routing number determines the identity of the institution involved in financial transactions.
A bank routing number is also known as a routing transit number or ABA number. Accuity serves as the official routing number registrar for the American Bankers Association (ABA).
Established in 1836, Accuity began as the publisher of the McFadden American Bank Directory, now known as the American Financial Directory. This publication provided key information about all 650 banks that existed in the U.S. in 1836, and today provides data about thousands of banks in over 150 countries.
In 1911, National Bank Routing Numbers were established in the United States by the ABA, and Accuity was named Official Registrar of the American Bankers Association. Almost 70 years later, in 1979, an electronic file system of ABA routing numbers was established.
In 1985, a Routing Number Administration Board was created by the ABA to administer routing number policies.
The joint task force was also established to enforce the eligibility criteria for obtaining a routing number, as well as establish guidelines for assigning and administering routing numbers.
ABA routing numbers are only issued to Federal or State chartered financial institutions eligible to maintain accounts at Federal Reserve Banks. There are 12 Federal Reserve Districts including San Francisco, Dallas, Kansas City, Chicago, Minneapolis, Cleveland, St. Louis, Atlanta, Richmond, Philadelphia, New York, and Boston.
Bank Routing Numbers appear at the bottom of checks. A Routing Number is a nine-digit number consisting of three components (referred to as AABB CCC D).
The first component (AABB) consists of four numbers. The first two digits of the first component (AA) identify the type of financial institution. Digit values between 01-12 indicate banks. Values between 21-32 indicate savings & loans or credit unions. 61-72 indicates electronic transactions. 80 is for travelers checks. The second two digits (BB) of the first component is the identifier for the specific Federal Reserve Bank District branch.
The second component (CCCC) also consists of four numbers. These numbers identify the specific ABA institution on which the check is drawn.
The third component (D) is a single check digit that is calculated according to a specifically calculated mathematical algorithmic formula. Its chief purpose is to act as a verifier for routing number accuracy. Note that there are software calculation programs made specifically to calculate check digits.
Canadian Bank Routing Numbers have a different structure format (AAAAA BBB) than American Bank Routing Numbers. They're regulated by the Canadian Payments Association.
The first component (AAAAA) consists of five numbers and acts as an identifier for the specific bank branch. The second component (BBB) consists of three numbers that identify the specific bank institution (i.e. Bank of Montreal).
If a bank is purchased by another bank, the routing number on a client checking account will have to change. Note that bank takeovers will typically schedule a transition period where old routing numbers remain in force until new numbers are established. A client using checks with old routing numbers risk bounced check penalties.
Checking accounts can be fraudulently compromised if someone gains access to your routing number along with your checking account number.
Regular routing numbers serve to identify the bank and its associated presentment point. Note that the presentment point must be in the same availability zone as the banks principal office.
A bank may also have a separate routing number for electronic transactions. Routing numbers for electronic transactions are administered by the Automated Clearing House (ACH) to process credit and debit automated transactions. Banks may also have a separate routing number for travelers checks and wire transfers as well.