What Social services are increasingly commissioned under quasi-markets, in which providers from all sectors compete for public service contracts. However, despite the intuitive rationale that open bidding facilitates better services and more consumer choice, the marketisation of social care has been criticised for relying on principles of new public management, which are often accused of prioritising cost-effectiveness above service quality. Yet, little is known about how the mixed provision of social care influences service delivery. This project sets out to investigate the unique features of for-profit, public, and non-profit sector providers of social care and to develop a theoretical framework of how these characteristics can be thought to influence social care services. Why To meet the growing demand for elderly care services, in part due to the ageing population, the modern welfare state is under pressure to innovate existing social care provisions. A common attempt to optimise these services is by privatising social care and by allocating public resources according to free bidding across for-profit, public, and non-profit providers. However, the terminology and underlying meaning of ‘sector’ and ‘ownership’ is subject to different conceptualisations across different fields of research, making it challenging to optimise regulation and funding to support the mixed social care provision effectively. It is the ambition of this project to develop a revised theory of ownership in the context of social care services. How To develop a theory of the mixed provision of social services, this project will undertake a theory synthesis to develop an up-to-date and comprehensive theoretical framework outlining the distinctive features of for-profit, public, and non-profit sector social care providers. This framework will then be tested through qualitative semi-structured interviews with UK social care providers to refine the outcome of the theory synthesis to ensure that it reflects and is informed by actual practice. SSR This project will develop and refine an interdisciplinary theoretical framework that will conceptualise the unique factors influencing for-profit, public, and non-profit sector social service providers. Such insights will have important implications for policy, in that an improved understanding of the distinct characteristics of different providers will enable policy-makers to address potential ownership-specific challenges through regulation. Further, this work will constitute a substantial contribution to the existing literature by mapping the converging and diverging characteristics influencing different provider types.