Digitalisation and the changing world of work are calling into question the standard employment model as a basis for social security systems. Whilst a growing number of publications deal with the consequences for industrial relations and labour law, social law is still being left out of most research projects on digital work. This book aims at widening the perspective. It concentrates on the two most important questions in the context of social protection in a digitalised world, namely access to social protection systems and their future financing, putting emphasis on platform work. It gives an overview of different national approaches to these questions, it analyses the respective solutions in a comparative manner, and it puts them into a transnational context. By bringing together case studies from Belgium, Italy, the United Kingdom, the Netherlands, Denmark, Sweden, Spain, France and Estonia and addressing the specific reform challenges for EU standard setting, EU coordination and the relation to tax law, the book provides new insights on what a "Social Law 4.0" should look like.