Medicare comprises 12 percent of the federal budget and is the third largest federal program after defense and Social Security. For fiscal year 2011, HHS reported an estimate of almost $29 billion in Medicare FFS improper payments. Our Standards for Internal Control in the Federal Government suggests that agencies should continually perform monitoring activities to reduce the incidence of improper payments.15 However, our prior reports found weaknesses in CMS's monitoring of Medicare provider and supplier enrollment and claims payment contractors.