This paper analyzes the arguments that in the absence of legal regulation, our case law has invoked to assign retroactive effects – ex tunc­ or future effects – ex nunc – to the sentences of annulment of administrative acts, ranging from assimilation of the latter with civil legal acts to the alleged identity of the general administrative act with the law, all framed within what has been understood by consolidated legal situations. This study demonstrates that retroactive or non-retroactive activity is not a necessary and automatic condition of the sentence of annulment of the administrative act because this idea cancels important reflections that deal with weighting basic principles such as the guarantee of efficiency, legal certainty, substantive justice, legitimate expectations and equality. In order to understand that the temporary effects of sentences do not derive from any formality of the process or of the administrative act nature or the type of sentence; these are rather one of the tools so the judge can- through modulation in each case- give efficiency to its sentence and meet the obligations that are imposed by the constitution and the law which has its only purpose in guaranteeing the protection of fundamental rights and preserving the legal order.