ABA routing transit number

In the United States, an ABA routing transit number (ABA RTN) is a nine-digit code printed on the bottom of checks to identify the financial institution on which it was drawn. The American Bankers Association (ABA) developed the system in 1910^[1] to facilitate the sorting, bundling, and delivering of paper checks to the drawer's (check writer's) bank for debit to the drawer's account.

Newer electronic payment methods continue to rely on ABA RTNs to identify the paying bank or other financial institution. The Federal Reserve Bank uses ABA RTNs in processing Fedwire funds transfers. The ACH Network also uses ABA RTNs in processing direct deposits, bill payments, and other automated money transfers.