40 Pa.C.S. § 3805

If an insurer retroactively denies reimbursement for services as a result of coordination of benefits under the provisions of section 3804(4) (relating to exceptions to retroactive denial of reimbursement), the health care provider shall have 12 months from the date of the denial, unless the entity responsible for payment permits a longer time period, to submit a claim for reimbursement for the service to such entities.