A Merchant Identification Number (MID) is a unique identification number assigned to a merchant account by a payment processor or acquiring bank. It is used to identify the merchant when processing electronic transactions, such as credit card payments.

The MID is typically a nine-digit number that is associated with the merchant’s bank account and is used to track the movement of funds between the customer, the merchant, and the acquiring bank. Each MID is unique and is assigned to a specific merchant, so it cannot be used by any other business.

The MID is an essential part of the payment processing system and is used to ensure that transactions are properly routed and settled. It also helps to protect against fraud by allowing the payment processor to track transactions and identify any suspicious activity.