Regardless of the amount of damage that is caused by someone rear ending you, you need to handle the situation in a serious manner. If your car is totaled or there are just a few scratches, it is still important to involve your insurance company as well as the insurance company of the other individual involved.
It is not a smart idea to not get your insurance company involved, even if the other person is requesting just that. If an insurance carrier is not contacted, you are left at the mercy of the other driver. It is then very possible and easy for them to dip out on covering the cost of the damages that they had caused. Getting both parties insurance involved as quickly as possible helps to get you the best coverage possible, resulting in quick repairs and costs being covered without issue.
Once the accident has happened and you have checked both parties for injuries, you need to contact the police. No matter how much damage resulted from the accident, the police are necessary in validating an insurance claim. They are able to provide legal documentation that is required by all insurance companies to move forward with a claim. Police can also be helpful in keeping the communication peaceful and under control. Do not leave all the responsibility to the police though. Make sure that you are in possession of the other parties insurance and contact information. The best way to get this information is by keeping a calm and friendly demeanor, regardless of how frustrated you may be with the circumstances surrounding the accident. Important pieces of information to gather are names of both the driver and the owner of the vehicle, phone numbers and addresses, copies of driver licenses information and license plate numbers. Gathering their insurance information is also incredibly important. Make sure to get the name of the company they are insured by, their insurance claims information and make sure to copy down all information from their insurance card.
In this day and age it is quite easy to snap photos of video documentation of the damage for later proof. You should also immediately write down and document all circumstances and possible reasons for the collision. Having all this information will help to settle all insurance claims in a timely manner.