Look at the bottom left corner of your checks. If you have a Personal account the first sequence of numbers, usually a nine-digit number, is your ABA (American Bankers Association) routing number. If you have a Business account the ABA number will follow the six-digit check number at the bottom of your checks. The ABA number is also known as a Routing and Transit Number, RTN, or bank number. It was established by the American Bankers Association to identify the accountholder’s bank when processing checks or depositing money to an account.