This Opinion Statement of the CFE ECJ Task Force analyses the ECJ’s decision in Brisal and KBC Finance Ireland (Case C-18/15) of 13 July 2016. Following a Portuguese reference for a preliminary ruling, the Court’s decision provides further clarification on the permissibility of withholding taxation within the European Union. In relation to interest, the Court held that non-resident taxpayers may be subject to withholding taxes (even if comparable residents pursuing the same activity are not) but that non-residents may nevertheless not be taxed on gross income (when comparable residents are taxed on net profits) and are, therefore, entitled to deduct expenses directly connected to their business activity.