The purpose of this paper is to study the effect of the tax expenses on accounting conservatism on firms listed on Tehran Stock Exchange. In this study to measure the conservatism accruals is used to test the research hypotheses based on the information gathered from 61 firms listed on Tehran Stock Exchange over the period 2004-2009. Findings indicate that the relationship between conservatism accounting and corporate tax burden was positive and significant. In addition, firms with high book-tax conformity had higher motivation to use the conservative accounting to reduce their tax payments.