In its recent judgment inW AG the Court of Justice of the European Union (CJEU) fundamentally departed in substance from earlier case-law concerning the treatment of ‘final losses’ incurred by foreign permanent establishments. However, like in other tax cases before, the Court did not clarify that previous decisions (in particular, Lidl Belgium) are ‘overruled’ now. This causes unnecessary damage to legal certainty in the area of EU tax law, and the CJEU should reconsider this approach towards ‘overruling’ in future cases. Furthermore, situations of ‘overruling’ also deserve special attention within the framework of the current reform of the preliminary ruling system. overruling, legal certainty, direct taxation, final losses, Marks & Spencer doctrine, preliminary ruling, Court of Justice, General Court, Grand Chamber, CJEU Statute, CJEU Rules of Procedure