Purpose: The complexity of customer relationships has been recognized in the relationship marketing literature. Yet, the understanding of how this complexity impacts on the formation and development of different relationship forms is limited. Focusing on the development of customer-service provider relationships in a financial services context, this paper aims to critically examine the nature and formation of business-to-consumer service relationships. Design/methodology/approach: Qualitative methods were employed, with in-depth interviews undertaken with a sample of UK bank customers. Findings: The complexity of customer relationships was documented by approaching relationships as multidimensional, dynamic and contextual. A relationship typology based on four key relationship components (trust, commitment, buyer-seller bonds, and relationship benefits) is proposed. This typology suggests that for a relationship to exist it does not necessarily have to encompass an emotional dimension. Moreover, the paper demonstrates the importance of the fit between customers' relational expectations and their experiences with service providers in developing long-term committed relationships. Research limitations/implications: The study was limited to the UK context. The extension of this study to other sectors or financial institutions operating in different regulatory and technological environments needs to be tested. Practical implications: It is crucial that relationships are viewed as multidimensional, taking into account various relationship components. Since different relationship components influence relationships differently, organisations need to develop different relationship marketing strategies for each consumer segment according to consumers' relational expectations. Originality/value: Building on preceding research, this paper broadens understanding of the complexity of customer-firm relationships by presenting insight into the affective element of relationships and highlighting the role of the fit between customers' relational expectations and their experiences in relationship development. © Emerald Group Publishing Limited.