European Commission's corporate guidance on citizen engagement. The objective of this “Guidebook” is to establish a reference toolbox that identifies and categorises different formats of citizen engagement, from the fully-fledged citizens’ panels on pan-European level to other co-creation and exploratory formats. This corporate guidance aims at helping services to choose the most relevant methods of citizen engagement for their policy file and to understand better how to implement them and which added value they get from each of the citizen engagement formats described in the guidebook.