What was the pre-1997 statute of limitations for medicare reimbursement claims? For some reason I had it in my head that the statute of limitations mirrored the claims filing requirement under the plan. Is this correct? If so, where can I find the authority?

If the reimbursement request was generated prior to 1997, there was no legislated statute of limitations. You can dispute the debt by providing proof of the plan's timely filing limit, but that is not always accepted as a defense. Generally, proof of a timely filing limit is the plans' SPD and plan document, HMO certificate of coverage or any other "official" documents that states the time limit.