Routing transit number

An ABA routing transit number (ABA RTN) is a nine digit code, used in the United States, which appears on the bottom of negotiable instruments such as checks 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 checks 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.