The content of law depends on the understanding of its provisions. Interpreter of the law texts is sometimes in front of the dilemmas that a specific word contained in the mentioned text should be understood as the universal language, or as it is understood in the language of specialist law practitioners, e.g. technical (law) meaning. Technical meaning of some word sometimes vary then that word has in common. Proper choice between universal meaning and special meaning of some word might be a serious challenge for an interpreter, e.g. judge in tax case. The literature in the field of tax law often expressed view that in determining the meaning of the expressions of a legal text in the case of the difference should be rather preferred meanings from legal language than universal one. The main argument for this concept is the use of the existing acquis of legal doctrine and/or judiciary leads to achieve greater uniformity and consistency in judicial decisions. The article formulates important caveat to this approach, particularly as far as the guarantee function of the law is concerned. The taxpayer is not obliged to know neither doctrinal nor judicial review and language used. In addition, some interpretive misconceptions surprisingly often gain unequivocal applause of the courts, which suggests the existence of the required uniformity of view in understanding a particular word legal text contained.