In this study, we examine empirically whether the gap between the pre-tax income and the taxable income predicts simultaneously earnings management and tax management. Prior researches have begun to estimate several indictors of earnings quality. We extends this works by investigating whether the book-tax differences (BTD) provides information about managerial discretion. BTD can be used as an attribute of information quality and can contain incremental information for investors and users of financial reports of companies We compose a sample of 21 listed Tunisian firms over the 2003-2012 periods, we apply a statistical methodology implementing a linear panel regression. We develop a model in which we estimate abnormal BTD. All earnings and tax management activities are captures by our abnormal BTD indicator (ABTD). From this regression we are going to test the effect of the variables of the earnings and tax management on the ABTD variable. We find, as expected, a significant association between BTD and manager discretion proxies. Our results indicate that BTD contains a predictive power over the earnings and tax management. We find that Tunisian companies are concerned about tax reducing rather than improved information quality and increasing the financial result.