This paper tries to identify factors that can reduce company marginal tax rate and debt tax advantage. In this order, at first Iran's tax codes were investigated and three main groups of factors that can reduce company marginal tax rate, were identified. The groups consist of revenues structure, expenses structure, and other exemptions used by the firms. Then the relationship among debt tax advantage, which belongs to expenses structure, with revenues structure and other exemptions used by the firms, were examined. The examination was made by using a multiple regression model and sampling data for 160 firm-years from tax returns of some firms which listed in Tehran stock exchange during 1998-2005. The results indicate that, as were predicted, use of debt is decreased as corporate tax rate is reduced. The results also show that, in contrast to the prediction, debt is positively related to export revenue, stock exchange revenue, and revenue of investing in other firms which are proxies for non debt tax shields.