Merchants who accept specific credit cards typically pay fees to the credit card companies for access to their validation systems during transactions. The validation process involves merchants sending card information to the credit card company, which then returns a simple acceptance or decline response without revealing the reason for a decline. This system is designed to protect cardholder privacy, requiring the cardholder to contact their issuer for details on any issues.Merchants may need to register with credit card companies to access these services, and they often work with intermediaries or "middlemen" like payment processors that handle multiple brands. These middlemen may have agreements with banks to facilitate transactions and could potentially receive payments from banks for promoting their cards. The relationship between credit card brands and issuing banks is complex, involving negotiations and agreements to ensure brand visibility and access to the validation systems.