ec.europa.eu (27.07.2023) Undeclared work has important economic and social implications, including the loss of social security contributions and taxes, but also higher incidence of work accidents, missed professional development opportunities for workers, unfair competition and market distortions for businesses, among others. The European Commission launched this study to gather deeper insights into, and empirical evidence of, successful policies and policy combinations for tackling undeclared work. This study reviewed empirical evidence across the full range of direct and indirect policy measures, including their potential effectiveness in transforming undeclared work into declared work.