When a complaint with regard to the commission of a cognizable offence is given to the police station, the police registers a First Information Report (FIR) on the basis of such complaint, in accordance with Section 154 of the Criminal Procedure Code. Such report under Section 154 Cr.P.C. is popularly called FIR. Thereafter, investigation is conducted by police in the offence(s) mentioned in such FIR. On completion of the investigation, if the police finds sufficient evidence in support of the offence(s) mentioned in FIR, it files charge sheet before the court under Section 173 Cr.P.C. against the accused persons. Meanwhile, during investigation, police may also arrest the accused persons. The prosecution or trial in such a case is conducted by the State (through public prosecutor, etc.).
On the other hand, where a complaint is directly submitted in the court by a person and if the court takes cognizance of the same and proceeds further on the basis of such complaint, it is generally called private complaint. A private complaint may in respect of a cognizable offence or a non-cognizable offence. The prosecution or the trial against the accused persons is conducted in such a case by the complainant himself (or through his advocate), who has filed such private complaint.
What is indicated above is the basic difference between the FIR and private complaint.
Dr. Ashok Dhamija is a New Delhi based Supreme Court Advocate and author of law books. Read more about him by clicking here. List of his Forum Replies. List of his other articles. List of his Quora Answers. List of his YouTube Videos.