This work explores the main distortions arising from the economic double taxation of distributed profits in three member states of the European Union: Portugal, the United Kingdom, and the Netherlands. The author analyses the tax implications of this form of double taxation from a legal point of view. To this end, Taxing Corporate Profits in the EU examines both domestic laws and international tax treaties covering inward and outward investment and dividend income tax burdens regarding those taxes that directly influence the effective dividend income tax rate. The author assesses the results of this analysis in light of the tax principles of neutrality; efficiency; non-discrimination under EU law; and the objectives of fair distribution of revenue between member states, simplicity, and prevention of tax evasion. The multi-faceted conclusion reveals that: Well-accepted tax principles, such as the principles of worldwide taxation and vertical equity, operate less efficiently within the overall tax system. Instead, the source principle is gaining momentum, with simplicity and neutrality aims prevailing over distributional criteria. The principle of capital import neutrality is of growing importance as compared with the principle of capital export neutrality. Problems remain with regard to the balance between debt financing and equity financing, unless an exemption system is in place, further complicated by the more favourable treatment given to capital gains. Neither classical nor imputation systems provide a satisfactory answer to these problems. Its comprehensive, comparative analysis makes Taxing Corporate Profits in the EU a valuable research work for academics and practitioners in the field.