The Commission has started an infringement procedure against Belgium because of withholding taxes for payments to enterprises not registered in Belgium which render services in the construction business in Belgium. On April 6th 2006, Advocate General Tizzano has delivered his Opinion in this case. The opinion seems to be less surprising than far reaching. As the Advocate General points out, a system like the Belgian one constitutes an obstacle to border-crossing services within the EU and therefore leads to an infringement of the freedom to provide services as enshrined in Art. 49 of the EC Treaty. The author analyses the opinion of the Advocate General and shows the consequences this case can have on special withholding taxes for non-residents in general, as they are provided in most of the member states of the EU. Interesting conclusions can be drawn from this case, if the ECJ follows the Opinion of its Advocate General. Especially in the light of the directive for mutual assistance in the recovery of tax claims between the member states, the space for discriminating withholding taxes at source seems to become more and more limited within the European Union.