Taxation is one of the most important economic issues in every community. Before the adoption of the
amendment, the average tax rate on companies based on Article 131 was about 64%. Calculating method of
companies’ income tax was received by virtue of article 131 of the act as follow: in the beginning 10% of
company’s taxable income will be received, the rest of it will transfer to the direct tax article 131 table and up to
45% of taxable income will be computed, and also at the time of dividing the profits between shareholders, a
double taxation will be deducted. Tax paying in the above mentioned way has led to inefficient economy and
shareholders may reduce their liquidity (cash) and investments, so for solving this problem direct tax act has
modified and many alternations had occurred on 2002/02/16; including applying a fixed rate equal to 25% and
considering the appropriate dispensation but the main issue is monitoring the changes occurred in listed
companies in stock exchange in Tehran caused by direct tax act modification in 2002 and the issues that change
this flat rate for the companies.