A merchant verification number, or merchant identification number, is a unique number assigned to a merchant that allows credit card and electronic payment companies to identify the merchant who is making the charge to the customer's account, says U.S. Merchant Systems. This number is used during all electronic transactions.
Before a company can begin accepting credit cards and other forms of electronic payment, it must have an assigned merchant identification number, says TransFirst. Each merchant location, according to U.S. Merchant Systems, must have its own unique number, not just one number per company. This includes any online shops a merchant may run, says TransFirst.