The provisions of the Tax Ordinance make use of the tax matter notion quite often, but in several different meanings. One of them was used by the legislator while indicating the scope of authorization for general and specific powers of attorney in the provisions, which came into force on 1 January, 2016. The term of tax matter appeared, among others, in Article 138e of Tax Ordinance, according to which the special power of attorney authorizes to act in the specified tax case or other case, belonging to the jurisdiction of the same tax authority. The functioning of the provisions on special power of attorney and the lack of a legal definition of the tax case, within which the attorney operates, revealed a number of interpretation doubts of this term in practice. The aim of this article — due to the ongoing judicial discussions — is to determine how to understand this term? Does the term "tax matter" used by legislator in the context of Article 138e § 1 of the Tax Ordinance mean the case in the material or procedural meaning? In other words, within the meaning of that provision, does a tax matter arise only at the very moment of initiating tax proceedings or does it exist earlier, regardless of the procedural aspect?