A routing number is a nine-digit code that identifies a bank, credit union or other depository institution in the United States so that payments reach the right place. Its formal names are ABA routing number and routing transit number (RTN). The full explanation of how the number is built and used is in ABA Number.
The routing number appears at the bottom left of a US cheque and is needed for direct deposits, ACH payments and Fedwire transfers. It identifies the institution, not the customer, so it is always paid together with an account number. Some banks use different routing numbers for ACH and wires, so customers are advised to check which one to use. For payments coming from abroad, banks identify each other with a SWIFT code instead.
Last updated 05 Nov 2026