In order to determine in which state the business profits of an international enterprises should be taxed, the term “permanent establishment” (PE) as defined in Art. 5 of the OECD Model Tax Convention (OECD MC) is of utmost importance. Changes in business models are giving rise to increasing attention as to whether enterprises have passed the threshold for having permanent establishments in host countries. The OECD has a project underway to clarify issues of interpretation of Art. 5 of the OECD MC. The project is characterized as a review of interpretational issues and not a fundamental re-thinking of Art. 5 or the concept of PEs. The conclusions of the OECD Committee on Fiscal Affairs’ Working Party 1 are expected to be introduced into the next revision of the Commentary to the OECD MC to be expected in 2013. Stefan Bendlinger highlights the PE questions which the OECD intends to clarify and which already influence Austrian tax treaty negotiations.