An ABA number, also known as a bank routing number or routing transfer number, is a sequence of nine numeric characters used by banks to identify specific financial institutions in the United States. The ABA Routing Number was developed by the American Bankers Association in 1910 to identify the specific financial institution responsible for the payment of a negotiable instrument. It is printed on the bottom left-hand side of checks and is used for domestic wires within the U.S. and international wires destined for an account within the U.S. .

While ABA routing numbers are used for paper or check transfers, ACH routing numbers are used for electronic transfers between financial institutions. The first two digits of ACH routing numbers often range from 61 to 72, which distinguishes them from ABA routing numbers. Transactions using ACH routing numbers clear faster (same or next day) than funds transferred on paper checks using ABA numbers. ACH transactions move more because they are done in batches instead of one at a time like an ABA routing number on a paper check.

To find your personal or business routing number, you can look at the bottom left of your checks, log in to your banking app, look at your bank statement, or call or visit your banking branch.