Streszcz. ang. s. 816. Bibliogr. s. 823-824

In order to ensure the effective functioning of the EU internal market, in particular the exercise of its freedoms, it is necessary to harmonize indirect taxes at the level of European Union law. This harmonization also covers excise duty. At the same time, when analyzing the harmonization of excise duty in the EU Member States, certain gradually emerging differences can be noticed at the level of national legislation. As a consequence, it should be considered whether they are the beginning of deharmonization processes and strengthening the tax sovereignty of EU Member States, which may become a major challenge for the tax law of the European Union overtime. The article discusses the idea of indirect tax harmonization at the European Union level, indicates the specificity of the harmonization of excise duty, presents contemporary deharmonization tendencies of excise duty in European Union law, as well as presents contemporary challenges related to the issue of excise duty in European Union law. The analysis of this issue was based on the following research methods characteristic for legal sciences: theoretical-legal, formal-dogmatic, literature criticism and comparative-legal method. Using these methods, it was concluded that there are contemporary deharmonization tendencies in the field of excise tax which are connected with legal, political, economic, financial, social, cultural and ecological conditions. Moreover, it has been noted that although the de-harmonization tendency is not yet universal, it is slowly affecting the functioning of the common internal market in the European Union. The problem of excise duty de-harmonization noticed by the authors of this article is a challenge for common economic and legal turnover in the European Union. The aim of the article is to analyze the harmonization and deharmonization trends in excise duty from the perspective of the European Union law, as well as to identify challenges for the EU legislation in this area.