An ABA routing number is a unique identifying code given to financial institutions that are located in the United States. As of 2015, the ABA number is made up of nine numbers and is used for various financial transactions, such as direct deposits, tax payments and e-checks.
The ABA routing number is provided by the American Bankers Association to each financial institution. When a transaction is made, the ABA routing number is used to identify the financial institution from which the transaction is being made. As of 2015, the ABA routing number can be found on the bottom left corner of certain types of checks alongside the account number.