An account number is a serialized identifier which is ascribed to a particular account holder or account at a financial institution, retailer, or other entity.

Account numbers may include letters or numbers and may be of various length, but they usually exceed 5 characters. An account number is a way for a company or organization to uniquely identify the accounts associated with each individual customer.

Account numbers can be assigned to sales and service accounts at various retailers, or to banking and investment accounts at financial institutions, or to membership organizations, among others. Part of the benefit of account numbers is a degree of anonymity or ambiguity which separates the identity of the account holder from the account information.

If a security breach were to access account number and balances, it might not be enough information to make withdrawals, for instance. This segmentation and restricted access to all of the information at once is a security benefit which can prevent identity theft from occurring.