摘要：The present study has as objective to analyze the concept of sovereignty, the existence or not of the sovereignty tax in Brazil and its implications on the federative pact and abilities taxes on MERCOSUR. It stands out the concern of one of the freedoms of the block, the free circulation of goods and services. The sovereignty of the State lodges the fiscal sovereignty or tax. In international scope, the fiscal sovereignty or tax is reflected as full capacity of a State ahead of excessively in the international scene. The State has fiscal sovereignty when it edits its laws, when its will is the last one to prevail how much to managed it's, and the fiscal sovereignty exceeds the territory of the State, when its ability tax reaches its contributors where it wants that they are. The applicability of the constant norms in International Treatys elapses the postulate of sovereignty, as concern the juridical power, which its concept discloses a supremacy character, distinguishing itself from the sovereignty of the State directed to all of its territory and in the reciprocal relations between the States. After that, treaty and the tax treaty are analysed more deeply. Such implications reflect in Brazil’s Reformation Tax and the adjustments assumed by MERCOSUR’s members.
