Aid architecture can be complex. Support Units of the National Authorising Officers (NAO) of the European Development Fund (EDF) have a large history, and some were founded about 40 years ago. Yet, analysis shows that they have not significantly evolved over the last ten years. This report identifies best practices related to EU work with its partner countries' aid management systems. Notably, it underlines new ways and means supportive to capacity development, and that could help in creating incentives for a renewed cooperation amongst national institutions and EU Delegations.