Structured Abstract:Purpose This paper contrasts two approaches to the study of contracts in business and industrial marketing: First, as a legal document in shaping at the outset exchanges and interactions, for instance in projects; and Second, as relational norms in becoming integrated into a business relationship through interactions, for instance as a resource. Approach The paper draws on cross-case comparison of three projects as actors develop an engineering service for optimising the maintenance of large-scale capital equipment by analysing data acquired from user records and in real time from sensors. Comparison is by coding interview and observational data as micro-sequences of interactions among actors. Findings Preparing contracts allows a project to commence and is an early form of interaction, intensifying new relationships, or cutting into and recasting established ones. Relational norms augment and can supersede the early focus on the contract, so incorporating incremental innovation and absorbing some uncertainties. Limitations The research approach benefits from detailed comparison and captures some variety across its three cases, but our discussion is limited to theoretical generalization. Practical Implications Our analysis and discussion highlights and focuses on when different approaches to understanding contracting are more apparent across durable business relationships. Transitions from a contractual document to a view of relational norms are subtle, vulnerable and not always made successfully. Originality This paper's originality is in it comparison of overlapping approaches to understanding businesses' uses of contacts in business and industrial marketing, of contract and relational norms. It develops a valuable research proposition, in the transition from a mainly contractual to a mainly relational uses of contracts, so identifying contract as a particular business resource, to be deployed and embedded.