The GAO reports that CMS and its contractors have not used the historical Hospital Payment Monitoring Program (HPMP) and Comprehensive Error Rate Testing (CERT) program error rates to identify and focus on “error-prone providers,” which GAO defines as providers that had at least one error in each of the four years of its audit period. The GAO consequently recommends that CMS: (1) use available error rate data to identify error-prone providers, (2) require error-prone providers to identify the root causes of claim errors and to develop and implement corrective action plans, (3) monitor provider-specific corrective action plans, and (4) share error rate data with its contractors to assist in identifying improper payments. CMS concurred with the recommendations.