A check gives direct permission for other banks to access your checking account funds. In order to tap those funds, the bank that receives the check must go through a verification process. Though the account number is extremely important to the completion of this process, the transaction cannot proceed without the check routing number.
What is a Routing Number?
When you're routing someone to your home, you give them the full address, which is linked to one specific place on the map. The same concept is in play when it comes to bank account routing numbers. A routing number identifies one particular bank out of many so that the processing bank --- the bank that presents the check for cashing --- can locate the account. Think of the check as a small map and the routing number as the identifier that leads another bank to the exact place where you hold an account.
Location on Checks
The routing number is commonly located across the bottom of a standard check. You may see a small graphic printed first, then a nine-digit code, which is the routing number. Your account number is printed next, followed by the check number.
A bank routing number routes the processing bank to your account number so that the bank can make a withdrawal. When the processing bank representative receives the check from a customer, he runs the routing number and account number through an electronic system to verify funds. After verification is complete, the bank listed on the check withdraws the funds requested and sends it to the processing bank.
It is possible for one bank to have multiple routing numbers. Small banks may just have one routing number to cover all branches but some banks, usually the larger national ones, have regionally assigned routing numbers. It is possible that your particular bank branch may print a different number on your checks than a branch in the next state over.