ABA Transit Number
What it is:
An ABA transit number is a unique identifier assigned to banking institutions by the American Bankers Association (ABA).
How it works (Example):
For those banks and banking institutions that qualify as account holders with the Federal Reserve, the ABA grants an identification number called an ABA transit number. A bank's ABA transit number has nine digits and always appears near the bottom left of its checks. The ABA transit number tells the Federal Reserve bank which commercial bank the associated funds will be withdrawn from.
The ABA transit number is followed by the individual account number and the number of the check itself. For instance, the bottom of check might read "623852453 1234567 001." The first nine digits make up the ABA transit number, the second seven digits are the account number, and the last three digits are the check number.