The OIG has issued a report on Medicare beneficiary copayment costs for outpatient services provided at critical access hospitals (CAH). Beneficiaries who receive services at CAHs pay Medicare coinsurance amounts based on CAH charges, in contrast to patients at acute care hospitals who are responsible for coinsurance amounts based on outpatient prospective payment system (OPPS) rates. According to the OIG report, “Medicare Beneficiaries Paid Nearly Half of the Costs for Outpatient Services at Critical Access Hospitals,” CAH charges are typically higher than the reasonable costs associated with CAH services or the OPPS rates that acute-care hospitals receive. The OIG estimates that Medicare beneficiaries paid nearly half the costs for outpatient services at CAHs in 2012 (approximately $1.5 billion of the estimated $3.2 billion cost for CAH outpatient services). The OIG recommends that CMS seek legislative authority to modify how coinsurance is calculated for outpatient services received at CAHs to reduce the percentage of costs paid by Medicare beneficiaries in coinsurance. For instance, CMS could consider (1) computing coinsurance so that it is based on interim payment rates rather than charges, and (2) processing claims for outpatient services at CAHs as if they were paid under OPPS for the purpose of calculating an OPPS equivalent coinsurance.