This paper studies the welfare effects of coordinated domestic sales tax reform associated with a reduction of the import tariff under imperfect competition. We set up a simple oligopoly trading model where domestic and exporting firms compete in the home market. We show that, if the initial levels of import tariff and sales tax are positive, there always exist welfare‐improving sales tax reforms. In some cases, a reduction of the sales tax accompanied by a reduction of the import tariff increases social welfare, whereas in other cases, raising the sales tax can increase social welfare.