An ABA routing number is a nine-digit code used by financial institutions in the United States to identify the specific financial institution responsible for the payment of a negotiable instrument, such as a check. The American Bankers Association (ABA) developed the ABA routing number system in 1910. The ABA routing number is printed on the bottom of checks and is the left-most number, followed by the account number and then the check number.

The ABA routing number system is managed by Accuity, which is the Official Routing Number Registrar and is responsible for assigning ABA routing transit numbers and managing the ABA RTN system. An ABA routing number can be issued only to a federal or state-chartered financial institution that has been determined to be eligible for a master account by a Federal Reserve Bank. The assignment of a routing number does not expand or change in any way the powers of the financial institution as specified in its charter.

To find your routing number, you can check the bottom of your checks, log into your account and select the desired account, select the account options link, select account information, and you will see the last four digits of your account number which links to the full account number and the routing number.