In this article, Stefan Pregesbauer analyzes a decision by the Austrian Federal Fiscal Court (BFG) concerning the denial of the principal residence exemption under Sec 30 para 2 no 1 lit b Individual Income Tax Act to a Nigerian diplomat employed by the OPEC Fund in Vienna. The tax authorities rejected the exemption on the grounds that diplomats are only subject to limited tax liability in Austria and therefore cannot claim a domestic residence. The court upheld this view, emphasizing that unlimited tax liability is a prerequisite for the exemption. This decision raises legal uncertainty for diplomats, especially since Austrian administrative guidelines (EStR) do not explicitly exclude them from having a principal residence. The author examines the legal foundations for tax privileges of diplomats and international officials, the interpretation of “residence” under Austrian tax law, and challenges the assumption that tax treaty-based privileges automatically imply limited tax liability under national law.