Human services, such as social supports and health care, have low contractibility; services are difficult to specify and measure, and difficult to manage when delivered by a third party. Services can and do fail, resulting in the inefficient use of public resources and potential harm to clients. This article develops a conceptual framing using transaction cost economics (TCE) theory to understand why human services are difficult to contract, and management control theory to understand how services might be managed. This identifies a potential tension between how low contractible services are managed when probity requirements are high. This is explored using a qualitative case study of an intermediary model of outsourcing, focusing on one of 31 Primary Health Networks tasked to commission primary health care under contract to the Australian Government. This study explains how design choices, making use of controls available in different organisational contexts across the intermediary model, overcame the tension between low contractibility and probity. This study adds to our understanding of the TCE characteristic of probity. A greater understanding of why this intermediary modelThis is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.