One of the most pervasive biases is overconfidence, which causes people to overestimate their knowledge and skills and underestimate their risks, and feel that they have control over issues and events, when in reality this may not be the case. Overconfident CEOs use their position and influence in their companies to achieve personal ambitions, which can be accompanied by aggressive tax policies, paying lower taxes, and showing higher earnings associated with CEO compensation. Therefore, overconfident CEOs are more prone to aggressive decisions. Meanwhile, audit committees are designed to act independently and resolve conflicts between managers and external managers regarding financial information and choices of accounting methods. Hence, the purpose of the research is to investigate the impact of the audit committee on the relationship between managers' overconfidence. And the tax avoidance of companies admitted to Tehran Stock Exchange is between 2014 and 2019. To test the hypotheses, multivariate linear regression and combined data were used, and the results showed that managers' overconfidence has a significant relationship with tax avoidance, and this relationship is direct, that is, with the increase of managers' overconfidence, the company's tax avoidance also increases. Also, in other findings of the research, it was observed that the audit committee (financial expertise of the audit committee) has a significant effect on the relationship between overconfidence of managers and tax avoidance of the company, and this effect is reversed, that is, the more the audit committee uses financial expert members, the relationship between overconfidence Directors and corporate tax avoidance will decrease.