To be in compliance with your contract, you need to notify your insurance company about a car accident promptly. Exactly how “promptly” is defined varies depending on the insurance company, but in general, you want to notify them as soon as possible to prevent your claim from being denied.
However, when making this notification, be careful. Tell them the facts of what happened and answer their questions as succinctly as you can. Don’t volunteer any extra information. Don’t talk about your injuries in detail, either. “I am getting medical treatment” is enough.
If the other driver’s insurance company contacts you, you are not required to talk to them at all. Remember, Montana is a “fault” state, which means the insurance company for the at-fault driver is generally responsible for paying for an accident. They have a financial incentive to downplay your claim or dispute who was at fault for the accident, and they will use any information you give them for that purpose.