In this globalised world, we could venture to say that it is impossible for tax regulations to keep pace with the development of society and, therefore, with the needs of the law. As a result, several gaps and loopholes are opening up in our legal system which can lead to abuse of the law in tax matters, especially in terms of tax avoidance and evasion. To combat this problem typical of international law, several tools have been created, including the beneficial owner clause. The aim of this paper is to delve deeper into this concept, to try to delimit what is meant by beneficial owner, a term that has not always been so clear and, in fact, has given rise to several jurisdictional debates. In order to achieve this, we will look at the fundamental role played by interpretation in law, analysing the most paradigmatic judgments in both the national and international spheres.