We recently treated a patient with non-life threatening injuries due to a MVA. We verified patients insurance and given authorization to treat. We then filed the claim to the patients auto insurance company with the following: 1)The insurance companies single page form that is actually a checklist to insure all information is included; 2) HCFA1500; 3) Doctors notes. Claim was filed within 24 hours of visit and insurance company recieved and processed the claim seven days from date of service. The auto insurance company denied the claim because I failed to list the principle diagnosis on their 1 page check list form, however, the attached HCFA did include all info. Now the insurance company says we do not have a second chance to file this claim correctly. They claim that this would be fraud to add this info after the initial filing. Has anyone ever faced this situation and if so, how did you deal with it?