The research aimed to investigate the impact of audit quality on the difference between declared and assessed taxes for companies listed on the Tehran Stock Exchange. A sample of۱۰۵ companies admitted to the exchange during ۲۰۱۰-۲۰۲۰ was selected, following defined restrictions. The research is applied in terms of purpose and descriptive-regression in terms ofdata collection. The hypothesis of the research was tested using eviews software, and diagnostic tests were conducted to establish the classical assumptions of regression. The dependent variable in the research is the difference between declared tax and assessed tax,while the independent variable is audit quality, measured by the tenure of the auditor. The research also considered control variables such as company size, return on assets, lever ageratio, ratio of market value to book value of shares, operating cash flow, and effective tax rate.The results of the research indicate that audit quality, as measured by the tenure of the auditor,has a positive and significant effect on the difference between declared and assessed taxes.This suggests that companies with longer - tenured auditors tend to have a smaller difference between the taxes they declare and the taxes assessed by the authorities. Overall, the research highlights the importance of audit quality in reducing tax disputes and improving the accuracy of declared taxes. It suggests that companies with longer-tenured auditors may have better tax compliance and reporting practices.