Technological and industrial developments have increased the diversity of commercial transactions and have begun to make businesses vulnerable to error and fraud. Errors and tricks negatively affect businesses' assets, their decisions, and even the continuity of the business. An effective internal control system is required to detect and prevent mistakes and frauds in businesses. TTK has not introduced a clear regulation on internal control applications to business owners. Indirectly, though not directly, the presence of some reference to internal control can be mentioned. TTK (Turkish Commercial Code) also gives information about internal control by the applicator. In the study, a questionnaire study was conducted to determine the effect of the internal control over accounting errors and tricks. In the questionnaire, proposals related to the basic functions of the participant were presented. A questionnaire was applied to 44 enterprises operating in the fields of trade, production and services in Gaziantep with an internal control system. The data are interpreted in descriptive statistical context. As a result, possible errors and tricks in the business have been found to be a significant influence of the internal control system in the prevention.