What principles underlie the tax administration's power to impose taxes and what prospects would allow tax matters, in particular tax doctrine, to be less of an obstacle to legality in Congolese law? The requirement of legality of taxation acts on the one hand and, on the other hand, the conformity of the tax administration's action to the legislator's will and the protection of the taxpayer due to the financial consequences of the interpretation adopted by the tax administration constitute the two major axes of this work. These two axes have been examined in the light of the legal provisions that have an impact on the taxpayer's legal security against changes in tax doctrine, mainly Article 39 of Law No. 04/2003 of 13 March 2003 on the reform of tax procedures as amended and supplemented to date.