Since 1970, the debate on the relationship between taxation and corporate financial performance has intensified during these last decades. The aim of this paper is to examine this relationship thesis. If it is acknowledged that incentives become a widespread method in the world in order to promote the investment, the paper contribute to the literature by testing the effects of an inciting taxation on the profitability of the Tunisian exporting firms in the sector of the Mechanical and Electric Engineering Industries. The empirical study, conducted on a sample of 60 firms, reports the following results: the estimation of the benefit and the output conclude that an increase of taxation affects negatively these two financial criteria of the performance. In addition to the use of temporal data, an approach based on an investigation by questionnaire confirms the results found at the time of the other approaches.