CMS estimates that $48 billion of estimated Medicare outlays of $509 billion in fiscal 2010 went to improper payments, including fraudulent ones. “However, this improper payment estimate did not include all of the program’s risk since it did not include improper payments in its Part D prescription drug benefit, for which the agency has not yet estimated a total amount,” said Kathleen King, director of GAO’s health care team.

Officials said it’s also much harder to identify how much of the improper payments were caused by fraud, which left some GOP lawmakers at the hearing frustrated.

“If you can’t identify it, you can’t penetrate it down,” subcommittee Chairman Cliff Stearns (R-Fla.) said. He said it is “incomprehensible” that CMS can’t estimate the level of fraud in the program.