In this article, the author explains that it seems that, based on ECJ case law, the “good faith principle” has become a prerequisite for taxable persons in order to be able to deduct the input VAT they have incurred. After explaining the legal requirements for deducting input VAT that are set in both the VAT Directive and the Polish VAT Law, the author provides a deep analysis of the Stehcemp case, focusing on the concept of good faith given by the ECJ in this and previous cases and also examinig the potential impact of this decision on Polish law.