ABA Number Law and Legal Definition

ABA transit number is an identification number assigned by the American Bankers Association (ABA) to banks and savings associations. ABA number is a nine-digit number. The number appears on U.S. checks in the lower left-hand corner. ABA number consists of a two-part code. The first part shows the location and the second identifies the bank itself. In order to qualify for an ABA transit number, the financial institution must be eligible to hold an account at a Federal Reserve Bank. The number is used in sorting and clearing checks. It is also used to identify the bank facilitating the payment of the check.