A letter report issued by the Government Accountability Office with an abstract that begins "Medicare claims are screened against enrollment information, using automated enrollment-related prepayment edits, in an effort to prevent improper payments to ineligible providers and suppliers—such as those that are no longer active in the Medicare program or are not properly licensed to provide the services for which they have submitted claims. Officials with the contractors we interviewed described the use of several types of prepayment edits to ensure that claims data are valid. For example, verification edits are intended to check the provider’s National Provider Identifier (NPI), which indicates whether the claim was submitted by an active provider or supplier. However, factors such as the frequency with which contractors have updated provider and supplier enrollment information and limitations of the data used may affect the timeliness and accuracy of data used to screen claims—in turn limiting the ability of the edits to prevent improper payments from occurring. For example, to update information maintained in the Provider Enrollment, Chain and Ownership System (PECOS)—CMS’s centralized database for Medicare enrollment information—the contractors have relied on a variety of data sources that vary in the frequency with which they are updated …