The intense competition in e-commerce makes many small- and medium-sized retailers striving for dynamic pricing. Therefore, the core functionalities of a dynamic pricing system are investigated using single case study research method. They embrace both external and internal factors for price calculation. First, there are functions to get external information such as price information from competing retailers. They provide important information for calculation and forecasting. Second, internal oriented functions exist, which analyse personal information such as the birthday in order to influence the buyers’ decisions in a positive way.