The Court of Justice of the European Union (CJEU) ruled that the national treatment provision in Article 49 Treaty on the Functioning of the European Union precludes Member States from disallowing consolidation between entities resident in the same Member State, where the top holding or intermediate holding company is resident in another Member State. After the United Kingdom left the EU from 1 January 2021, this case law no longer directly applies to situations with a top holding or intermediate holding company resident in the United Kingdom. However, the Trade and Cooperation Agreement concluded and in force between the EU and the United Kingdom (TCA) contains in Article 129 a provision on national treatment. The authors argue that the TCA could be interpreted in line with the national treatment provision in Article 49 TFEU and the case law of the CJEU on this. Notwithstanding the absence of any direct effect to the provision of the TCA, Member States should interpret their bilateral tax treaties in line with the TCA. The consequence is that the non-discrimination provisions in existing bilateral tax treaties between Member States and the United Kingdom should be interpreted in line with the TCA.