This book explores the concept of beneficial ownership in equity law, and in the domestic tax laws of the United Kingdom, Canada and the United States; as well as its varied and increasing uses in international tax law. By analysing the evolution of beneficiary rights in equity and the use of beneficial ownership wording in tax law, the book draws a roadmap for dealing with beneficial ownership in tax law and international tax law. This approach highlights those common misconceptions that can be avoided by understanding the origins of the concept and its engagement with equity, as well as the differences with tax law. However, the book does not limit itself to dealing with theoretical discussion, but also offers an instructive and detailed practical case study. Offering both academic commentary and a practitioner focus, the book will be of the utmost interest to practitioners and scholars from common and civil law countries dealing with tax and estate law, particularly given beneficial ownership's increasing relevance.