The gender pay gap (GPG) exists in every European country, but it varies considerably, even in EU member states covered by the same legal principles on pay equality. Part of the variation can be explained by different patterns of social partnership. With current policy pressure to de-centralise collective bargaining and increase the percentage of pay linked to productivity, what role can social partnership play in tackling the GPG? Reporting on the findings of the European Commission funded research project "Close the Deal, Fill the Gap", this book uses an interdisciplinary analysis involving legal, economic, and sociological expertise, to explore the role of social partnership in GPG in Italy, Poland and the UK. Selected on the basis of their contrasting profiles in terms of legal regulation, industrial relations, systems of collective bargaining, coverage of collective agreements, and differing rates of the GPG, the in-depth study provides important insights into the main issues underlying the problem of reducing the gender pay gap which have led to guidelines in the negotiation of arrangements on GPG-related issues. Based on a unique comparative, interdisciplinary and action-oriented esearch project, it will be of great interest to all researchers and advanced students with an interest in women’s representation in the workforce and the gender pay gap, as well as practitioners and policy makers in organisations such as trade unions and employers’ associations.