1. Complain to the force
Every force must record and handle complaints, and it costs nothing. What it gets you is an explanation, sometimes an apology, and occasionally a finding against an officer. What it does not get you is compensation.
The force investigates itself, which is why the next step matters.
2. Apply for a review if you are not satisfied
If the force's answer does not stand up, you can apply for a review. Depending on the type of complaint that review is carried out either by your local policing body, which is the Police and Crime Commissioner's office, or by the Independent Office for Police Conduct. The decision letter from the force tells you which applies to you, and applying to the wrong one wastes time.
It is worth doing. Across all forces reporting, 24.5% of completed reviews found the force's own outcome was not reasonable and proportionate. Close to one in four.
See how often your force's decisions are overturned.
3. Bring a civil claim
A civil claim is separate from the complaints system and is the only route that results in compensation. It covers wrongful arrest, unlawful detention, unlawful stop and search, trespass, malicious prosecution, and injury caused by excessive force.
Start with your force
How a complaint is handled varies enormously between forces, and so does how often those decisions survive review.