The first few moments following an auto accident can be an extremely confusing, emotional, and frightening time. As such, it may be difficult to know what accidents need to be reported and what your insurance may require.
There are some types of accidents that will always need a response from one of the local law enforcement departments, such as Highway Patrol, Police, or Sheriff. Each law enforcement department will have a jurisdiction, meaning that which department responds and takes the report will depend on where the accident occurred. For example, an accident within the city limits will most always be handled by the Police. Regardless of the responding department, you should always make a report when an auto accident involves elements like an injured person, severe damage to any vehicle, and/or a driver flees the scene of the accident.
Your insurance company may also require you stay on the scene and report the accident, even in cases where the other driver flees the scene of the accident. Some insurers will accept a counter report. A counter report may be provided by the responding officer for you to fill out, or you might need to go to the nearest station to complete the form off scene. Counter reports are fairly commonplace in larger jurisdictions when the responding officer sees that the vehicles involved are still in working order and no one is injured. In any event, just make sure to remember to get a copy of the counter report for your insurance carrier.
Even if the accident doesn't involve one of the above elements, there are certain situations where it can be very helpful to have a law enforcement response and accident report. For example, the other driver might admit blame and offer you cash for your damages, but refuse to give you his/her insurance information or contact information. Even if the other driver does offer you his personal contact information in such a situation, you still have no way of knowing if the information being provided is factual. Another example would be you forgetting to collect all the important information and crucial details of the accident because you're stressed or confused from the accident.
Making a police report can be very helpful in any of these situations since it will involve the law enforcement officer collecting/verifying the driver's name, address, phone number, car tag, insurance information, accident details, injury details, and so forth. Basically, most any detail that would be needed in court or by the insurance adjuster will be documented in the police report.
Lastly, even though a police report will be necessary or needed for many accidents, you should still always try to remember to write down all the information yourself. Depending on the jurisdiction, it can often take weeks to months for the insurance adjuster to request and obtain a copy of the accident report. On the other hand, the adjuster can initiate the investigation immediately when you're able to provide the insurance information on the other driver(s).