Account Number

A unique code that is assigned to the account owner for ease of reference in a financial institution’s accounting records

What is an Account Number?

An account number is a unique code composed of numbers, letters, or other characters, and is assigned to the account owner for ease of reference in a financial institution’s accounting records.


Account Number



  • An account number is a unique identifier that works alongside a routing number to identify an individual’s account, as well as a particular financial institution.
  • Modern technology-oriented enterprises use two-step verification passwords as a way of minimizing risks on users’ accounts.
  • The account number is used to route a request of financial authorization to the correct owner before granting access, thereby facilitating various types of commercial transactions.


The most common type of account number is a checking account number, which identifies the owner and grants access, facilitating various forms of commercial transactions. It is issued to the payment processor and used to route transaction authorization requests to the appropriate owner.

An identifier with a similar role to the account number is the Social Security Number, where the sole purpose is to monitor the earnings history of U.S. workers to determine their benefit entitlements. Nowadays, the checking account number is used across the world to make financial transactions.


How an Account Number Works

In the case of a paper check, the account number is normally indicated at the bottom between the routing number and check number. The first group of numbers, from left, indicates the 9-digit routing number, the middle is the account number, while the third group is the check number.

The arrangement system dates back to 1910 when it was developed to ease the sorting of checks before assigning them to the correct owners. The account number is used in the same function to make payments to the correct party. However, the check number can sometimes be switched with the account number.

Checking account numbers are used by payroll processing agencies to create a direct payment system for workers. Account numbers are linked to the majority of financial transactions that merchants make. Items such as credit card accounts, sales receipts, or gym memberships come with account numbers.


Account Number vs. Routing Number

Identifying a customer during a bank-related financial transaction requires two relevant pieces of data – the account number and the routing number. The unique set of information is assigned when opening an account at a financial institution.

An account number is specific to the account holder and is akin to a customer’s fingerprint or ID. Similarly, the routing number includes unique numerical codes that can identify each banking institution, facilitated by the International Bank Account Number (IBAN).

IBAN follows a structure of checking digits to facilitate sanity check, which is all about detecting and eliminating instances of duplicated, omitted, or mistyped characters. It allows validation at the point of data entry where a program validates the account number, number of characters, account number format, and country code.

The data is uniquely assigned to the owner to indicate the source and destinations during a financial transaction. For example, an account number and a routing number must be issued to the relevant financial institutions before electronic funds transfer.

In the U.S., the routing number takes a nine-digit format, which proves that the identified financial institution not only maintains an account with the Federal Reserve but is also state- or federal-chartered. It is more often used during tax payment or when reordering checks.

An account number, on the other hand, is used jointly with the routing number to identify a customer’s digital account. Furthermore, it comprises between eight and twelve digits. If a customer is holding dual accounts in the same bank, the bank account number will be different, while the routing number will be similar.


Protecting Account Numbers From Fraud

As is the case with passwords, account numbers are also highly exposed to fraud and identity theft. It explains why a series of annoying questions constrain the routine change of an account number.

Further modifications are currently taking place to make it even less vulnerable to hackers. For example, password managers, combined with the multi-factor authentication system, make it difficult to bypass security features.

Modern techno-savvy enterprises usually protect their customers’ accounts by employing an overly complex master password to gain access to customer account numbers and other highly classified and sensitive data.

Also, accounts with multi-factor authentication, which includes a second security layer to protect an account, are becoming the norm. For example, customers are required to provide biometric data, voice-activation, or a time-sensitive code sent to their email or mobile phone when accessing their accounts.

Regardless, the security enhancement features are not entirely foolproof. Hackers can still gain unauthorized access to accounts when they acquire authentication factors.

Some of the methods to intercept such data include using malware, an account recovery procedure, or phishing. Modern businesses are striving to protect users’ account numbers in an online environment that is increasingly vulnerable.


More Resources

CFI is the official provider of the Commercial Banking & Credit Analyst (CBCA)™ certification program, designed to transform anyone into a world-class financial analyst.

To keep learning and developing your knowledge of financial analysis, we highly recommend the additional resources below:

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