Abstract: This study addresses the issue of mechanisms and tools for combating and investigating fraud in financial reporting, in the context of an amplification of this phenomenon over the last decades. The aim of the paper is to highlight the importance of the internal control system in this area, by reference to the most widespread formal framework for the implementation of the internal control system, namely the COSO model. The analysis undertaken is limited to providing an overview of the main concerns of financial auditors in relation to internal controls in terms of the key audit issues revealed in the audit report over a period of five years. Through this analysis, we wish to draw attention to the limitations of the internal control system and the need for awareness of the ethical factor in decision-making.