The Massachusetts Executive Office of Health and Human Services, Office of Medicaid (State agency), did not always use the correct Federal medical assistance percentages (FMAPs) when processing claim adjustments reported on the Quarterly Medicaid Statement of Expenditures for the Medical Assistance Program (Form CMS-64). As a result, the State agency received approximately $106 million (Federal share) more than it was entitled to. The State agency used incorrect FMAPs because it processed adjusted claims as current expenditures for both public and private providers. We recommended that the State agency refund approximately $106 million to the Federal Government and ensure that it processes future adjustments in accordance with Federal requirements. The State agency partially concurred with our recommendations.