A lei complementar em Direto Tributário e o risco ao Federalismo Fiscal: os limites para a lei complementar dispor sobre conflitos de competência e estabelecer normas gerais

Abstract

The Constituent opted to reserve certain essential topics related to the Tax System established by the 1988 Federal Constitution for regulation by complementary law. As a technique for national coordination between the federative entities, the following functions stand out: (i) resolving conflicts of competence in tax matters between the federative entities and (ii) establishing general norms regarding tax legislation (Article 146, items I and III, of the Federal Constitution). This paper aims to analyze the topic based on the constitutional framework of complementary tax law, with the goal of demonstrating that dysfunctions in the matter can lead to issues from the perspective of Fiscal Federalism and, in extreme cases, undermine the tax competence of federative entities. To this end, it investigates the fiscal interface of the federative state structure and the National Tax System, including the prohibition on granting heteronomous exemptions under Article 151, III. Furthermore, the paper seeks to define the characteristics of complementary tax law, based on essential concepts for the study of the topic and the historical context of this regulatory instrument in Brazilian Law. Additionally, after examining the functions of complementary law related to Federalism, as already highlighted, it analyzes federative conflicts brought before the Federal Supreme Court, where the underlying issue involved the interference of complementary law in the competence of States and Municipalities or the failure to enact necessary complementary law for the exercise of the competence of these entities. Finally, the paper seeks to study the topic within the scope of the Tax Reform implemented by Constitutional Amendment nº 132/2023 and regulated, thus far, by Complementary Law nº 214/2025.