Expert power is based on the awareness that a person in a power relationship possesses valuable knowledge, information, or skills (Raven, 1992, 2008). It builds customer trust, long-term relationships, customer satisfaction, loyalty, and exit barriers. The buyer´s preferences for a product or solution are shaped by sales force expert power (Doney & Cannon, 1997; Clauss & Bouncken, 2018). With these preferences, the buyer participates in the decision-making process, where the mechanisms of organisational buying find application. However, what remains unclear is which attributes a buying centre specifically associates with sales force expert power, when and how the perception of sales force expert power alters in the buying process, also which factors are responsible for it are issues that have not yet been discussed in the context of group decision-making in buying centres, and finally to what extent does sales force expert power influences the decision frame of each member of the buying centre. To address these gaps, the aim of the study is to create an approach by which sales forces can consciously manage and enhance the clients´ perceptions of sales force expert power. For this purpose, Alpha Software customers from various industries were interviewed immediately after their purchase decision regarding the perception of sales force expert power and what influence this perception had on the buying centre’s decision. The findings of the study indicate an overload of sales force expert power can lead to mistrust and uncertainty. The perception of sales force expert power is important in all stages of the buying process. In early stages product knowledge is perceived more strongly while the perception of change knowledge in final stages predominates. Information exchange and recommendations lose their impact due to an unprofessional approach to change which minimises the perception of expert power significantly. Due to the intensity of change and how the change is perceived the perception of sales force expert power alters. Business customers, unlike consumers, expect a professional approach to change rather than benevolence. The interviewed clients perceive the software conversion project as a change project and expect the sales force to be approached and addressed accordingly. Change knowledge is cited as an important attribute for sales force expert power, which can advance the clients´ perceptions of sales force expert power.