Abstract Background User involvement and participation in the supervision of the quality of care is an important topic for many healthcare inspectorates. It offers regulators an additional view on quality, increases the legitimacy and accountability of the inspectorate, empowers users and enhancing the public’s trust in the inspectorate. To assess the accessibility of the local governmental social domain services the Joint Inspectorate Social Domain in the Netherlands worked together with people with intellectual disabilities performing as ‘mystery guests’ in an innovative project. This paper describes the findings of the evaluation of this project. Methods People with intellectual disabilities living at home on their own may need some help with daily activities such as administrative tasks, raising children, household tasks, managing debts or finding work. In the Netherlands they have to arrange this help at their municipality. The goal of this project was to find out how easily people with intellectual ...