Resumen
Principle of legal security is based upon the principle of legality in some legal systems, while in some others, it is positioned opposite to the same principle, under the meaning of principle of legitimate confidence. In the introduction section of this article, the principle of legal certainty is defined and the special importance of legal security in the field of taxation is clarified. The security provided by the principle of legality and the principle of legitimate confidence are synthesized mostly with quotes from court decisions, in the main body of the article. The discussion on which principle to be prioritised when both principles come across is addressed in the final section.