Since the publication of the previous edition of this work, there have been considerable developments in the law on administrative procedure. These developments have been promoted on the one hand by the digitalization of administrative work and communications, and on the other by overlaps with European Union law. These have made a fourth edition of the commentary necessary. The book is still committed to the goal of presenting a manageable and consistent volume that avoids unnecessary ballast and deals with the relevant problems within a manageable space & for those involved in practical work in particular, but also for students and academics. The new edition systematizes and comments not only on national developments in case law, but also on developments in administrative procedural law at the European level.