Abstract

This paper attempted to answer the question of Product market structurefor client companies have any significant effect of the on auditing costs. Audit fees as Auditing Costs is independent variable and Product Market Structure indexes as dependent variable includes Herfindahl-Hirschman Index, Lerner Index, Modified Lerner index .Three main hypotheses to answer research questions and research goals were developed. The companies listed in Tehran Stock Exchange was used as the statistical community. To test the hypotheses panel data regression analysis was used. Block holders to enhance accountability and transparency, on the other hand managerial stock ownership with reduce the agency problems in the same way will increase and reduce audit costs.