Both concepts are regulated in the present law of Criminal justice from article 259 onwards and the main difference between both is interpreted in the legal formalities that must follow and the legal consequences they establish.

In both actions although the fundamental goal is to inform the competent authorities the commission of criminal acts, in the denunciation, the denouncer can inform anonymously the criminal act and not be part of the procedure. In addition, there is no need for a lawyer to be involved in this procedure, whereas in the complaint there are essential and minimum requirements to be followed which includes as part of the procedure identifying each part before the Competent Justice board.

The denunciation or formal complaint is the act by means of which ANY person who has been present at a crime or public criminal act must inform the police or Competent court, under penalty of fine if he/she does not to do so. This denunciation does not force the authority to initiate a judicial procedure.

The denunciations can be formalised by means of two routes: in written form or verbally. If the denunciation were presented or displayed in written form, it will have to be signed by the denouncer to give its conformity of the reflected content, whereas if it is verbal, it will be a legitimized civil public employee who will reflect the saying in an act that will be signed by both.

There are exceptions to the obligatory nature of presenting or display of a denunciation, in the case of young males under 14 years of age and young females under 12 years of age – denominated prepubescent -, in addition also those who do not have total mental capacity – denominated as disabled-. This exception also includes the spouses of the delinquent. Also lawyers will be exempt from denouncing those cases that their clients confess – denominated as professional secrecy to them without damage, all of which is regulated by European law that enforces it.

The complaint is the act by means of which ANY person, who feels as much affected by the commission of a crime – in person, as in its goods, communicates to a Criminal Justice board the existence of these presumed facts, showing in addition the will to be part in the process that begins consequently. Therefore, to present or display a complaint is not an obligation but a right of every citizen or victim that considers themselves offended by the practise of a crime.

There are formal requirements for the presentation of complaints, being the most important, that it will have to appear in written form – unlike the denunciation -, detailing the data of identification, relation and facts, to the Criminal Justice board its designated, and the diligence, prophylactic measures will prevent its practice. In addition, it is obligatory to be represented by a lawyer and the presentation of a guarantee depending on the case.