Natural language techniques have been employed in attempts to automatically translate legal texts, and specifically contracts, into formal models that allow automatic reasoning. However, such techniques suffer from incomplete coverage, typically resulting in parts of the text being left uninterpreted, and which, in turn, may result in the formal models failing to identify potential problems due to these unknown parts. In this paper we present a formal approach to deal with partiality, by syntactically and semantically permitting unknown subcontracts in an action-based deontic logic, with accompanying formal analysis techniques to enable reasoning under incomplete knowledge.