What Is an Account Number?

An account number is a unique string of numbers and, sometimes, letters and other characters that identifies the owner of a service and permits access to it. In the U.S., the Social Security number was the primary identifier until its vulnerability to identity theft forced the practice to be abandoned.

In today's electronic age, the most important account number for many people is the checking account number. Payroll processing offices use checking account numbers to set up direct deposit payments for employees.

How an Account Number Works

The account number is located on the bottom of the paper check. You'll see three sets of numbers in a computer-readable font at the bottom of the check:

  • The first number on the left is the nine-digit bank routing number
  • The middle number is your account number
  • The third number is the number of the check

Key Takeaways

  • An account number is a unique identifier of the owner of a service and permits access to it.
  • Account numbers are attached to virtually every transaction anyone makes.
  • In our electronic era, they are vulnerable to fraud.
  • Multi-factor identification and other security measures protect identification numbers as well as passwords.

Special Considerations on Account Numbers

In addition to checks, account numbers are attached to just about any transaction a consumer or business can make. Sales receipts, subscription services, credit card accounts, and store club memberships all have them.

The traditional check layout applies to most personal checks. Some business checks and bank-printed checks have other formats.

And identification numbers, in addition to passwords, are vulnerable to identity theft and fraud. This is why we have to answer annoying questions about our mothers' maiden names when we try to make routine changes to an account.

The means of making it difficult for hackers to steal account numbers currently are taking the form of password managers along with multi-factor authentication systems.

Modern businesses now often employ a hard-to-hack master password to unlock an electronic vault of customers' account numbers and other sensitive data. Consumers are becoming accustomed to multifactor authentication, which adds another step before accessing an account, such as a fingerprint, voice activation, or a time-sensitive code sent to the cellphone number on record.

These are just some of the means of protecting users’ account numbers in an increasingly vulnerable online environment.

Routing Number Vs. Account Number

The nine-digit routing number identifies specific financial institutions within the U.S. The number identifies the check as having been issued by a federal- or state-chartered bank that maintains an account with the Federal Reserve.

This system dates back to 1910 and was developed initially as a way to help bank clerks sort through piles of checks and assign them to the correct drawer. Today, electronic services use them in much the same way for wire transfers, to draw a payment from a deposit at the correct institution.

The account number works together with the routing number to identify the right account holder at the right institution.