This article deals with the relationship of the occupation administration of the Third Reich introduced in Upper Silesia in September 1939 to the issue of income tax for 1939. The article discusses the analysis of Polish legislation and case law in the field of tax law, the proposed regulation and its motives, and the final solution. Considerations concerning the Polish income tax were preceded by the presentation of analogous German measures taken in connection with the accession of Austria and Sudetenland.