According to Art. 5 para. 3 of the OECD Model Tax Convention (OECD-MTC) a building site or construction or installation project constitutes a permanent establishment (PE) only if it lasts more than twelve months. According to the OECD-Commentary on the MTC the twelve months threshold applies to each individual site or project. However such activities should be regarded as a single unit, even if based on several contracts, if forming a coherent whole commercially and geographically. In a decision dated November 19, 2003 referring to the German-Luxembourg Tax Treaty the German High Court decided that both a commercial and a geographical coherence must have been established to consider different construction and installation projects as a single unit for applying the twelve months test as per Art. 5 para. 3 OECD-MTC. The Court ruled that a geographical coherence is not deemed to exist if the contractor's activities are spread over the whole territory of a state. Stefan Bendlinger analyses the impacts of the High Court's decision on the taxation of international building and construction projects.