Making Complex Interfaces Work for the National Disability Insurance Scheme: street-level governance of funded supports coordinated with mainstream services (hereafter the Making Complex Interfaces Work project) was funded by the Australian Research Council (2019 to 2021). The purpose of the study was to explore the implementation and coordination of National Disability Insurance Scheme (NDIS) plans for NDIS Participants (henceforth Participants) with complex and severe impairments in South East Queensland, who were allocated funding for services and supports that could be sourced from multiple providers to reach their aspirations. Plan implementation in such circumstances often involves intermediary functionaries (NDIS plan managers and Support Coordinators), and multiple providers delivering discrete components of a Participant’s plan, and requires Participants, intermediaries, and providers to interact with mainstream services to advance plan implementation and Participant wellbeing. Such plan managing across multiple interfaces manifests multiple forms of complexity.