The innovative ‘mainstreaming approach’ for climate-related action is described and assessed, together with the ‘non-productive investments’ in the European Union. The recent European Court of Auditors’ recommendations and the European Commission’s reactions on these issues are carefully analysed. Both the European Funds and the national co-financing should provide support to promote sustainable goals in a cost-effective manner. The responsibilities to achieve this may vary for the EU and the Member States, depending on the direct or shared management mode applied. In response to the 2030 Agenda for Sustainable Development, the ‘quality’ of public spending should be improved, finding a balance between the robustness of data and the administrative effort required.