Most insurance companies allow up to a year for providers to submit a claim.
Anything later they typically will NOT cover no matter who is at fault for the delay. What will get you into trouble is the state statutes that could allow a business to bill you for services rendered much later than the insurance will cover. So, if they bill you after a year has gone by, your insurance isn't obligated to pay for it. And by signing the responsibility agreement at the time of service, you now are the responsible party for unpaid balances. I am having the same issue where I received a collections notice for services from over 5 years ago while under a different insurance company.