Transactional costs associated with providing professional services are reduced by allowing prospective patients/clients (bidders) and professional service providers to negotiate competitively for desired fees for proffered services through an interactive on-line communications network such as the Internet. A transaction system server handles online communications and procedures for conducting auctions for delivery of proffered services and maintains a registration database of service providers and bidders. An authentication/qualifier engine automatically researches and verifies service provider credentials and background information upon registration of a service provider with the system. A service feedback interface and database are provided for handling online feedback information and comments from patients/clients and providers regarding the complexity and quality of services received or provided.