The politics and tax legislation being a manifestation of strict sovereignty of the State, the phenomenon of double taxation occurs frequently representing a difficult poison for the foreign trade activity, especially hindering investments abroad, technology transfer or proliferation outside of the state of the companies’ branches. Therefore, international legal double taxation, by the repeated taxation of the income, it is an obstacle to the development of economic relations between states, reducing the revenue of the international operators and their interests in making investment abroad. This paper presents the main causes that determine double taxation, its forms, i.e. the economic double taxation and the international legal double taxation, the need for eliminating the double taxation and avoidance methods.