The paper examines the principle of equality as it is traditionally interpreted and applied in EU tax law, with the aim to understand to what extent it is necessary to reconceptualize it after the Lisbon Treaty and the introduction of the EU Charter, which makes fundamental andhuman rights and sustainable development binding principles for the Union .EU law is built on the principle of equality and on an interpretation of it that has economic origins relating it to the concept of formal equality, firmly tied to the creation of the Common Market in 1957 and to the European Economic Community (EEC) as a community of tradebased on the four fundamental freedoms. EU governance in matters of taxation as originallyframed in the Treaty of Rome was informed by this view, and led to a EU tax law frameworkaimed at ensuring equality in terms of competition on the one hand, and economic freedomson the other.

The introduction of binding concerns for fundamental and human rights and for sustainability as part of the EU legal framework implies the addition of a second, substantive dimension to the conceptualization of the right of equality which necessarily poses the issue of reassessingthe meaning and bearing of the concept itself. This paper investigates two of the grounding questions for a reassessment: how the principle of equality should be reconceptualized to account for its substantive dimension as required by the Lisbon Treaty and how said reconceptualization would affect the very foundations of the power to tax in the Union.