The main purpose of this research paper is to propose a methodology based on the COSO Report for implementing the diagnosis of the Internal Control System of the “Cajas Municipales de Ahorro y Crédito” (CMAC) from Trujillo city. A descriptive orientation was determined by giving a qualitative, analytical and interpretative approach to this research. The sampling method used was a non-probability sampling through a semistructured inquiry applied to 28 CMAC Trujillo’s colleagues with different job positions and duties from any of the 4 CMACs in Trujillo. By the other hand, referring to the documental sampling, the selected documents and managerial tools were among the following ones: Corporate Strategic Plan, Corporate Operating Plan, Organization and Functions Manual, Regulation on the Organization and Functions and the Structural Organizational Chart. After reviewing adventages y ...