This Practice Insight summarises lessons learned from four case studies conducted to examine what bearing the notion of ownership has on anti-corruption interventions involving the private sector. By demonstrating how effective ownership is often shared, and evolves over time as partners create results together, it promotes a more nuanced understanding of ownership than that expressed by documents such as the Paris Declaration and the Accra Accords. The recommendations provide guidance on assessing the appropriate scope and objectives of ownership for any development project.