An ABA routing transit number (ABA RTN) is a nine digit numerical code, used in the United States, which appears on the bottom of negotiable instruments such as cheques to identify the financial institution on which it was drawn. The ABA RTN was originally designed to facilitate the sorting, bundling, and shipment of paper cheques back to the drawer's (check writer's) account. As new payment methods were developed (ACH and Wire), the system was expanded to accommodate these payment methods.
The Routing Number is used for domestic transfer. To make money transfer, the Routing Number is used together with the bank account number of the recipient. For international inward money transfer, a SWIFT code must be used together with a Routing Number and Account Number.
The Routing Number is used by Federal Reserve Banks to process Fedwire funds transfers, and by the Automated Clearing House to process direct deposits, bill payments, and other such automated transfers.
The format of Routing Number is as follows:-