Routing Numbers, also known as ABA Numbers or Routing Transfer Numbers are 9 digit numbers used by the banking system in the United States for identifying. A routing number is a nine digit code, used in the United States to identify the financial institution. Routing numbers are used by Federal Reserve. Digits five through eight are used to identify the specific bank, such as USAA, Chase or TD Bank. The last digit is called the “check digit,” because. The checksum algorithm determines the ninth digit of the routing number and is used to validate the eight digits before it. Another possible usaa bank account number length is to look on the website for the state in which you currently reside. Your routing number says more about your account than the institution with which you bank. These are often used to validate software applications. Active, retired, and military veterans who were honorably discharged are eligible. Because you will have multiple banks at play during these transactions, your routing code will help eliminate confusion. Together, the first four numbers are called the Federal Reserve Processing Symbol.