The notion of tax has been transforming through centuries and it will continue to do so, because on evolutionary level, it changes with respect to public, political, economic and social changes. Getting to know the world and some distinct aspects of it, is the continuous way of deepening the knowledge, which explains the transformation and evolution of tax theories, as long as the base of it is deep. Along with development of finances, tax is defined as expense, payment, price; so, the authors of definition give different roles to taxes.