In Poland, for many years, administrative courts have adjudicated, among others, in tax cases using the in dubio pro tributario principle (the principle of the benefit of the doubt). This principle was not expressis verbis stated in the Polish legal norms. As of 1 January 2016, the legislator introduced in Article 2a of the Tax Ordinance a regulation that "doubts about the content of the tax law that cannot be removed shall be resolved in favour of the taxpayer". Since this rule became binding, questions have appeared as to how such a rule, formulated in this way, should be applied by tax and fiscal control authorities. The aim of this article is to discuss the application of this rule in practice, referring to the decisions of courts. The Author formulates conclusions resulting from the caselaw of courts and indicates at the same time the need to make changes to the provision of Article 2a of the Tax Ordinance. Therefore, de lege ferenda, he suggests changing the provision of Art. 2a of the Tax Ordinance as soon as possible and proposes a broader phrase that "all persons in any way obliged to bear tax burden shall have the right to resolve doubts in their favour".