A Merchant Category Code (MCC) is a four-digit number listed in ISO 18245 for retail financial services. MCC is used to classify the business by the type of goods or services it provides. MCCs are assigned by merchant type (eg 3000 for United Airlines).
A MCC is assigned to a merchant by the card company when the business first begins accepting cards as a form of payment.  The code reflects the primary category in which the merchant does business and may be used:
- By credit card companies to offer cash back rewards or reward points, for spending in specific categories.  
- (By Automated Fuel Dispenser (MCC 5542) have specific rules for authorization and clearing messages).
In the United States , it can be used to determine whether or not the Internal Revenue Service for tax purposes. 
- ISO 8583
- ISO 18245
- NAICS Code
- Standard Industrial Classification
- Jump up^ VISA. “Merchant Category Codes” (PDF) . Usa.visa.com . USA. Archived from the original (PDF) on July 10, 2007.
- Jump up^ Chase. “Welcome to AARP® Credit Card from Chase. Earn 3% cash back rewards are restaurant and gas station purchases Single (Terms)” . Chase Bank . Retrieved December 16, 2015 .
- Jump up^ Discover. “Credit card rewards that really add up” . Discover it . Retrieved December 16, 2015 .
- Jump up^ Internal Revenue Service (August 2, 2004). “Internal Revenue Bulletin: 2004-31, Rev. Proc 2004-43, Merchant Category Codes to Determine Reportable Payment Card Transactions” . IRS . USA.