The American Bankers Association maintains an online search tool for consumers to look up ABA routing transit numbers. To look up an ABA number, the user enters a financial institution name and a state, at minimum. A city and a ZIP code help to refine the search.
To access the search tool, the user clicks a button to agree to the fact that she is accessing the tool for personal use only. Commercial access to the search tool is not free. A successful search returns an institution's address and its nine-digit ABA number. ABA numbers identify banks and other financial institutions for check processing, electronic funds transfers, online banking services and other purposes.