The purpose of an internal audit is to provide advice and provide objective assurance on the effectiveness of the managerial internal control system by providing recommendations that ensure and contribute to improving the work of the public entity. By assessing systems, processes, high-risk activities in the presence of errors, fraud, irregularities or significant non-conformities. The reality shows that, depending on the determinants, synthesized in pressures, opportunities and attitudes, there are significant differences in the risk of fraud. Differences can be identified at different levels of the internal control system, areas of activity and in different times, between financial years. The risk of fraud and corruption must be managed by the entity's management but also regularly evaluated by the internal auditor in conducting audit engagements. The establishment, assessment of the control environment and the management of major risks with a high degree of fraud implies a concise mechanism of effective activities in the prevention of fraud and corruption at entity and process level. This article will outline the basics of fraud in the public entity, the assessment of fraud risk by internal auditors using non-statistical models and indicators.