We have identified the following overpayment and are in good faith voluntarily refunding all monies collected in error. Overpayments are Medicare funds that you or a beneficiary has received in excess of the amount allowed payable under the Medicare statute and regulations.An overpayment occurs when CMS pays a provider more than the amount due and payable according to existing laws and regulations. Use this guide to help you and your staff properly assess refund requests from health plans.