In this article we explore the claim that the four freedoms of the EU lead to the inevitable erosion of the capacity of Member States to collect tax, undermining national systems of welfare and solidarity. We argue that European tax integration has undergone a significant change during the last ten years or so, with a judicial, regulatory and legislative response by Union institutions. First, the Court of Justice has recalibrated some of the basic concepts it applies when reviewing the European constitutionality of national tax norms. Second, the Commission has utilised state aid rules to attack targeted tax competition. Third, important legislative initiatives have been adopted or proposed to safeguard Member State taxing capacities. The new phase is influenced by the changed constitutional context of the recent enlargements and the Eurozone crises, which may increase the supply of and demand for tax integration.