This paper checks the credibility factor in order to identify a coherent logical relationship of its application in the model of the Inflationary Targeting Regime (IMR) justifying it as an important assumption within this regime. Conceived within the theoretical framework of the new classical school, the concept, "credibility" in monetary policy, is increasingly studied and developed in the literature. Therefore, the aim of this paper is to verify this credibility factor under the proposition that it can be verified by the difference between expectations and inflation targets.