The specialization of companies' activities and the necessity of competition in the financial markets have caused companies to take measures in order to maximize their benefits. In this situation, companies may try not to pay additional taxes and pay less taxes as much as possible and institutionalize a process of earnings management. This earnings management can lead to tax differences. The tax difference is the result of the discrepancy between the final tax and the declared tax and can be caused by tax evasion or tax avoidance. Since the main mission of the internal audit unit is to provide independent and impartial assurance and consulting services in order to add value and improve the company's operations, the present research seeks to determine the effect of internal audit quality on tax disputes with the moderating role of the audit committee. The current research is applied in term of nature of research; in terms of type of research, it is causal, which is conducted via a descriptivecorrelation method and based on multivariable linear regression model, after systematic elimination, using the information of 120 companies during the years 2015 to 2019 in SPSS software. The results showed that the quality of the internal audit had a positive effect and the characteristics of the audit committee had a negative effect on the tax difference of companies listed in the Tehran Stock Exchange, and the characteristics of the audit committee moderated the relationship between the quality of the internal audit and the tax difference in a negative direction.