How long after an accident do you have to file a claim?

Please note that there is a difference between "filing a claim" and filing a law suit. Filing a claim is simply contacting the insurance company and getting the claim set up. That should be done immediately. Filing a law suit depends on what state you are in. That is regulated by the Statute of Limitations in that particular state. Since I can't tell what state your in, I can't tell you what the limitations are for you.