A new GAO report reviews CMS’s collection of Medicare Advantage (MA) encounter data, which includes detailed information on services and items furnished to enrollees. CMS plans to use MA encounter data in addition to current diagnosis data to risk adjust capitated payments to MA organizations in 2015. The GAO determined that CMS has not yet developed requirements for completeness and accuracy of the encounter data, nor has it performed statistical analyses that could detect complex data validity issues. The GAO recommends that CMS establish specific plans for using MA encounter data and thoroughly assess data completeness and accuracy before using the data to risk adjust payments or for other purposes.