When you need to file an FIR and the police officer you approach declines it on an unreasonable ground, then you can go and complain to the Senior Officer. If he also refuses from filing the FIR, then a written complaint can be made and then be presented to the Judicial Magistrate. Once you do this, the Judicial Magistrate will order the police to file the FIR. Nowadays E-filing of the complaint is possible.
After your complaint gets registered, make sure to take the receipt.
A police officer can deny filing an FIR on various grounds. One of the most common reasons is the issue is too ordinary or belongs to a different territorial jurisdiction. Crime is categorized into two classified terms- ‘Cognizable’ and then the ‘Non-Cognizable’ offences. The cases which fall under Cognizable terms are the ones where FIR can be filled, those who fall other Non-Cognizable need Magistrate order to take an action. Crimes like rape, dacoity, rioting, murder, etc fall under the Cognizable category, where police can arrest the culprit without a warrant. However, the Non-Cognizable crimes are Public Nuisance, cheating, forgery, fraud, etc, where a police officer can’t arrest anyone without a proper warrant.
As per law if you are not allowed to file an FIR related to any of the Cognizable offence which also falls under the same territory then under Sec 154(3), you can approach the Senior police officer or the Commissioner, and even the Superintendent of Police with a written complaint. The subordinate police will then direct a senior officer to file an FIR.
If your complaint is still not registered by the senior officer, then you can write a written complaint and give it to the closest magistrate U/s 156(3).