First Information Report (FIR) is a written document prepared by the police when they receive information about the commission of a cognizable offence. It is a report of information that reaches the police first in point of time and that is why it is called the First Information Report. It is generally a complaint lodged with the police by the victim of a cognizable offence or by someone on his/her behalf.
Anyone can report the commission of a cognizable offence either orally or in writing to the police. Even a telephonic message can be treated as an FIR.
It is a very important document as it sets the process of criminal justice in motion. It is only after the FIR is registered in the police station that the police take up investigation of the case.
An FIR is a report of a crime filed with the police to initiate the investigation process. However, an FIR cannot be registered for all crimes, and so it is important for one to know the crimes and circumstances in relation to which an FIR may be registered.