This article focuses on analyzing how the scope of certain constitutional principles has been amplified or reduced by the Constitutional Court at the moment of reviewing the legality of tax laws. Upon examination of the constitutional doctrine, the conclusion that follows is that the principles of equity, progressiveness and equality, and the principle of bona fide, have been applied in a restrictive way, whereas the extent of the efficiency principle has been greatly amplified. Also, the constitutional judge has been particularly careful in extending into taxation the range of the constitutional principles that regulate the legal effects of norms over time.