Both parties mutually agree to leave the scene of an accident and now wants to claim?

It is both parties responsibility to report any car accident immediately. Even if both parties agree to leave a scene, it's still against the law. Insurance companies are famous for finding reasons not to pay out money, and when you don't follow laws it makes it more than easy to have claims turned down. It's not a wise move to file a claim after leaving the scene, you both may be subjected to charges from you local law enforcement agencies. In most cases, presence of a law enforcement official is needed to determine fault. The best thing to do at this point is to move on, before you all get into trouble. You should never put yourself in a situation where you best option is NOT to remain at an accident scene.