This article argues the case for a holistic approach to tax treaty interpretation in respect of multiple authentic language texts, which is supported by Polish case law. In daily practice, courts rarely consider other language text(s). Established international doctrine sanctions this practice by maintaining that a comparison of text(s) would not be necessary for cases of ‘routine interpretation’. This state of affairs impairs international consistency of tax treaty interpretation and necessarily produces cases of treaty misapplication. Hence, it is all the more important to pay attention to case law in which a court has looked at other authentic text(s) – particularly when it has commented on the methodology of plurilingual treaty interpretation in a fundamental manner and not only used the other text(s) to resolve an ambiguity or confirm an interpretation based on the text in its own language. This article will outline and discuss the position developed by the Polish Supreme Administrative Court (NSA) which is congruent with the views developed by the present author elsewhere based on fundamental principles of public international law and considerations of systematic consistency.