Is it required either by law or insurance company to file a police report on an accident?

I can speak for the State of Indiana on this one. When two parties are involved in an accident and the TOTAL of damage to BOTH vehicles AND any third party property is $1,000.00 or more a police report is required(by law). A form called an SR-21 is also required in Indiana to be filled out and sent to the BMV within ten days or the drivers licenses of the non reporting party will be suspended. Insurance companies have their own guidelines that you agree to when you sign your policy. The prudent thing to do in any accident is to have a police report done as well as report it to your insuance company. One reason, being the phenomenon of damage increasing after the accident as well as the neck pain that seems to come about after the "victim" has been talking to friends and relatives.