This thesis aims at exploring the Trans-National Enterprise (TNE) as a leading business and economic actor at the international taxation level, and the legal (international tax) framework surrounding it. It is spread over eleven chapters within four main parts; the first part addresses the question of what is the TNE, why is it important, and what is the international tax law that governs it. The first chapter addresses the importance of the THE in the modern world (economy) and the tax implication of that role. The second presents the international tax system that governs the TNE, where the OECD Model Convention claims a significant part. The third chapter explores the notion of the THE and the prospects of applying the enterprise entity theory on the taxation of the THE members. Part two addresses the obstacles against applying the enterprise entity approach on the taxation of the TNE; the fourth chapter examines the legal principles that stand in the way of applying the enterprise entity theory, especially legal separation; the fifth chapter presents the OECD MC's position towards the principles of arm's length and legal separation. Part three addressesth e problems causedb y this attachmentt o arm's length and legal separation; chapter six explores the problems of international tax avoidance; chapter seven explorest he role of legal separationin the different tax treatmentb etweent he PE form and the subsidiaryf orm. Chaptere ight addressetsh e problem of entity classification. Part four explores the prospects of an alternative approach to the taxation of the THE from within the OECD MC, by examining the case for aggregation (consolidation) in chapter nine, and the case for a formula-based allocation (based on the profit split method) in chapter ten. Chapter eleven recapitulates the conclusions from the previous chapters reaching to the final conclusions.

The role of the Court of Justice of the European Union in the process of direct tax integration in the European Union (EU) has been widely discussed in the academic literature, while another important actor, the European Commission, has attracted much less attention. The Commission’s input is commonly perceived to be limited to the right of legislative initiative. This study questions such an oversimplified interpretation and draws a more nuanced picture of EU tax harmonisation by integrating an analysis of the complex regulatory approaches adopted by the Commission for the establishment and smooth functioning of the Internal Market. It is argued that the past decade brought a notable change in the Court-dominated pattern of direct tax integration. This change is apparent first in the evolution of enforcement strategies under Articles 258 and 260 TFEU; and second, in the increased reliance upon non-binding regulatory measures. Both developments have strengthened the role of the Commission, supplying it with more possibilities for influencing national direct tax systems, despite the reluctance of Member States to agree upon legislative harmonisation. Against this background, the procedural and substantive problems associated with these instruments require closer examination. The normative scope of this research covers the key procedural problems related to the infringement procedure and non-binding regulatory measures. The empirical component explores the Commission’s enforcement and coordination practices, drawing particular attention to two case studies: the tax treatment of losses in cross-border situations and exit taxation. Following the analysis of enforcement and coordination in the field of direct taxation, the study argues the need and proposes potential solutions for (i) the developing of a more comprehensive procedural framework for the infringement procedure and non-binding regulatory acts; (ii) the strengthening of accountability mechanisms; and (iii) the enhancing of the effectiveness of their application.