The advent of multilateralism in taxation has become a challenge inherent to globalisation. The integration of this legislation with EU law standards (Anti Tax Avoidance Directive 2016/1164) opens up new avenues for effective control and the fight against international tax evasion and avoidance. Concurrently, it is necessary to accommodate, analyse and integrate the new regulatory standards and the emergence of new administrative powers, with the demands derived from the respect and defence of the legal position of the taxpayers affected. This necessitates, firstly, an analysis of the legal status of taxpayers in the context of cross-border situations. Furthermore, it is essential to identify the fundamental rights and guarantees that correspond to taxpayers in accordance with the constitutional, international, and supranational orders. This will be followed by an examination of the mechanisms for the defence and effective restitution of this basic legal situation in the context of international cooperation.