This research intends to present the influence of COSO framework-guided internal control system in Jordan on curbing tax evasion. The questionnaire, designed to meet the study's goals, was divided into five sections, each containing ten questions based on literature reviews and theoretical frameworks. The target group included managers, department heads, supervisors, and assessors from both Income and Sales Tax Department (ISTD) divisions in Jordan; a total of 280 individuals were surveyed. Ultimately 250 responses were received with a rate of 89.3%, out of which 12 were deemed invalid leading to a final analysis sample size of 238 (representing 95.2%). Data analysis and hypothesis testing was carried out using SPSS software by the researchers after this stage was completed. The results of the study have shown that COSO-based internal control system has its impact on fighting tax evasion in Jordan by the system. This includes all components: the control environment, information and communication, risk assessment, control activities, and monitoring performance. The study emphasizes that these five components of COSO should be collectively implemented as their integration is essential to have a positive effect on combating tax evasion in Jordan. Among the recommendations were removing psychological barriers between ISTD and taxpayers; also restoration trust relationship between financial departments and taxpayers, retraining audit personnel, establishment of a tax audit mechanism governed by standards that ensure fairness and objectivity with integrity in the act of taxation; moreover implementing COSO internal control framework which consists of five components with ways developed for application at Income & Sales Tax Department in Jordan.