The 2003 Constitutional Amendment no. 42 brought important changes in the Constitution, adding the Article 146-A to the 1988 text. This innovation allows the legislator to establish special criteria for taxation in order to prevent imbalances in competition. Given the many ways this standard can be taken and relevant practical implications, especially in the current socioeconomic context, mister makes the study of taxation as a phenomenon of state intervention in the economy to encourage behaviors and as a tool to prevent competitive imbalances caused by failures of structural, behavioral and resulting market taxation itself. Thus, the method used was the literature research on the specific object of study, together with others that involve fundamental questions to the development of this test work. The theme explains the intimate relationship between Law and Economics, studies from these two branches of knowledge were examined. Furthermore, it was analyzed the pertinent legislation to the theme, including the legislative debates preceding the legislative changes and law cases that occasionally refers to the Article 146-A of the 1988 Constitution. It is necessary to point out that the studies and the court decisions about the art. 146-A are not abundant. We conclude that any understanding of this article must be limited by the development as constitutional aim, and by constitutional principles, especially those concerning the economic order, as the principles of free competition and tax neutrality, under the penalty of unconstitutional acts. Moreover, taxation used with the specific aim of preventing imbalances competitions hardly smacks impactful effect if applied in a isolated way, to a set of strategic measures that take into account their effects on the economy is necessary, so that the competition can be as healthy as possible and gets to contribute to national development. It is clear that the main issues on the formal and material aspects of the art. 146-A of the Constitution are in need of further study of the meaning and scope of that rule, which urges to be effected.