چکیده (انگلیسی):

ccording to direct tax code, financial statements should be prepared based on Generally
Accepted Accounting Standards since the needed information to calculate the tax is provided from legal
offices and audited financial statements. It is expected that the tax calculated by taxpayer be the same as
the one diagnosed by auditors. However, a difference is observed between these two in practice. Many
factors can affect the amount of taxes expressed by taxpayers. This in turn affects corporate tax
differences. Then, it is essential to examine these factors since they provide a better understanding of
the concept of income tax, a smaller difference between diagnostic tax and expressed tax, improvement
of quality of expressed tax. The present study aimed to investigate factors influencing the reduction in
difference between diagnostic tax and expressed tax. For this purpose, a sample composed of 130
companies listed in Tehran Stock Exchange for the 5-year period from 2008 to 2013 was examined.
Student's t-test was used to test the research hypotheses. The results showed a significant difference
between companies in terms of ownership concentration, the ratio of our board and existence of tax
article in the independent auditor's auditing report in terms of the difference between expressed tax and
diagnostic tax. However, there was no significant difference between companies with earnings
smoothing and companies with nonearning smoothing and companies with annual earnings
adjustments in terms of differences between expressed tax and diagnostic tax.