Complaint and Information:
In a complaint the allegation is made to a Magistrate with a view to his taking action under the Code. In information the allegation is made with the object of putting the police in motion in order to investigate a crime. A Magistrate, therefore, acts on a complaint because the complainant has prayed that action be taken by him under the Code.
He may proceed with the complaint under Section 200 or dismiss it under Section 203 of the Code after recording his reasons. If there is, in his judgment, no sufficient ground for proceeding. On the other hand, the Magistrate on receiving information acts on his own initiative. He is not asked in the latter case by anyone to issue process and need not record any reasons if he decides not to act on the information so received. Again, on a complaint the complainant is first examined on oath unless made by a public servant in the discharge of his official duty.
But in case of information the informant is not examined on oath.
Complaint and First Information:
In complaint the allegation is made orally or in writing to a Magistrate, but the first information is given to the police. A complaint may relate to a cognizable or non-cognizable offence, but first information must relate to a cognizable offence on the face of it. Then, a Magistrate takes cognizance of an offence on a complaint made to him, but he cannot do so on first information. And lastly, a complaint does not include the report of a police officer but the first information of an offence may be given by anybody, may be a police officer.