The Effect of Audit Market Concentration on Audit Report Lag and Auditor Tenure of Listed Companies in Tehran Stock Exchange

Changes in capital markets in recent years have increased the auditor's pivotal role in the areas of decision making. Thus, recognizing and clarifying the nature of the performance and services offered by audit firms and their costs are a new field of efficiency capital markets in the world. The purpose of this research is investigation of audit market concentration on audit report lag and auditor tenure of Listed Companies in Tehran Stock Exchange. In this research, 92 companies were surveyed from 2011 to 2017. In order to measure audit market concentration, audit tenure and audit report lag. indicators of  TOP4SHARE, Number of years accumulated since the beginning of the auditor's activity in the company and natural logarithm of  time interval between the end of the fiscal year and the date of audit report are used respectively. The results showed that both aspects of the audit market concentration, had a negative and significant effect on the delay of the audit report and the auditor's tenure period.