If you've been injured in an accident, it's important to notify anyone who may be responsible. You don't have to know who was at fault; you must simply think about who might have been at fault. Moreover, in the beginning you don't have to give the people involved, or their insurance companies, any detailed information about the accident or your injuries. All you have to do is let them know that there was an accident at a certain time and place, that you were injured, and that you intend to file a personal injury claim.
Before you can notify those responsible for an accident of your intention to file a claim, you must decide whom to notify. This usually depends on the type of accident in which you were involved. For example, after a vehicle accident you'll need to notify the drivers of all vehicles involved, the owners of the vehicles, the employers of the driver if the car was on company business, and your own insurance company -- and there may be others. Depending on the circumstances, each type of accident -- vehicle or slip and fall -- requires you to notify different sorts of people.
Once you have determined those who might be responsible for your accident, your next step is to write letters telling each of them that the accident happened and that you were injured. You may need to send more than one letter -- for example, one letter to the business where you fell and another to the person who owns the property.
Write a letter of notification even if the others involved have assured you that they will notify their insurance companies. Your notification should be a simple, typed letter giving only basic information and asking for a written response. It should not discuss fault or responsibility, or the extent of your injuries; you will get to those things later on.
For detailed information about what to include in a letter of notification, and sample letters, see How to Win Your Personal Injury Claim , by Joseph Matthews (Nolo).
The important thing about giving others notice and starting your claim is to not delay too long. While you need not give notice within any specific number of days following an accident (except for injury claims against government entities), it is always best to start early, within the first couple of weeks after the accident.
Also note that filing a notice of an injury accident with people or agencies does not obligate you to file a claim against them, but if you do file a claim later, they will not be able to say that the claim has unfairly surprised them.