In practice
The acquirer assigns the code during onboarding based on the merchant's primary activity. Issuers use it for authorization rules, rewards and spending controls; networks use it to apply category-specific obligations. The code list is standardized in ISO 18245, with network-specific variations. Look up codes in the MCC search.
Common confusion
An MCC describes what a business does, not how risky it is. Two merchants with the same code can receive very different underwriting outcomes.
Frequently asked questions
How many digits is an MCC?
Four digits.
Who assigns a merchant category code?
The acquirer or its processor, based on the merchant's primary business and card-network rules.