چکیده (انگلیسی):

ABSTRACT: The purpose of this research is to study the relation of the effective factors on decreasing tax
assertiveness and tax diagnostic difference. The study is based on the analysis of samples include 123 companies
listed in Tehran Stock Exchange for the period of 2008 to 2012. The samples are selected through the Systematic
Elimination Method. The applied statistical methods for analyzing the hypotheses include the multivariate
regression test and F statistics as well as step by step method. In this research , among factors which could be
effective on tax assertiveness and tax diagnostic difference, the Own Concentration, Outside directors ratio, income
smoothing, independent auditor reporting tax paragraph, prior years adjustments have been studied. The results
indicate that the only effectual factor on the tax assertiveness and tax diagnostic difference, among the others, is
the adjustments of prior years. In fact there is a meaningful relationship between the prior period adjustments and
tax assertiveness and tax diagnostic difference in the companies.