This paper presents the structure and contexts of transaction costs and competitive tendering. The model is proposed as the first step in the development of a causal link between transaction costs and competitive tendering in the public sector. It draws upon the theory of open systems to build a structural framework. Concepts relevant to transaction costs and competitive tendering in the public sector are integrated into this framework. The subsequent papers will add concepts to the model and demonstrate a generic model fit for public practitioners, decision-makers, academicians, and bidders (suppliers, contractors, and service providers) to carry out their procurement activities in a systematic and planned manner.