I worked in a medical billing office for nearly 10 years. It is not to late to file. You do need to move quickly. Most insurance companies offer a 90 day timely filing period but it varies (some only offer as little as 30 days). AetnaAetna usually offers 180 days. It is ALWAYS based off of the Date of Service UNLESS they have otherwise stated in a contract with the health care provider (that doesn't happen often). Start the process now and even if they reject your claim you'll have the ability dispute it with Aetna and get the claim paid.