Generally speaking, in the end it’s considered the patient’s responsibility to make sure that all medical bills are submitted to the health insurance company for reimbursement. However, the process is complicated and largely in the hands of medical providers, so things like this can happen. When they do happen, it stinks.
To summarize the problem as I understand it, the auto insurer paid a portion of your medical bill. The remainder should have been submitted to your health insurance company, but the medical provider was slow to do so. When they finally did, the claim was denied because it wasn’t submitted in a timely manner. Now the doctor’s office is billing you for what was really their oversight.
Here’s what I’d recommend:
First, contact your health insurance provider, explain the situation step by step, and ask if they will make an exception and process the claim despite the fact that it was late. They may be more inclined to do so if you – rather than the doctor’s office – ask them to.
If they won’t process the claim when submitted by the doctor’s office, ask them if you can pay the bill to the doctor’s office and then submit the claim to your insurer yourself. They may be willing to reimburse you directly.
Finally – ask your insurer if the doctor’s office is in-network and, if so, if they’re contractually allowed to bill you like this. If they’re an in-network provider, they may have been contractually obligated to submit the bill for you in a timely manner. If they failed to do so, they may be contractually obligated NOT to bill you for it, but just to eat the loss.
If none of these options works, well, then I’m afraid I can only recommend that you pay the bill yourself. Otherwise, you’ll likely get sent to collections, it could affect your credit, and it would probably be more trouble taking it to court than it’s worth. In the end, if the doctor’s office isn’t contractually prevented from billing you for a claim they were late to submit, the charge likely becomes your responsibility by law, since services were rendered to you.