The Justice Department’s years-long court battle to force UnitedHealth Group to return billions of dollars in alleged Medicare Advantage overpayments hit a major setback Monday when a special master ruled the government had failed to prove its case.

The case began with a whistleblower who said UnitedHealth bilked billions of dollars through the Medicare Advantage program.

UnitedHealth Group notched a major court win in a legal challenge over its Medicare Advantage billing practices that is stretching into its second decade. | UnitedHealth Group notched a major court win in a legal challenge over its Medicare Advantage billing practices that is stretching into its second decade.

UnitedHealth Group Inc. won a major finding in a long-running lawsuit in which the US Department of Justice claimed the company overbilled Medicare by at least $2.1 billion.

The Justice Department lacks evidence to support claims the company withheld Medicare Advantage funds, a legal expert overseeing the case said.

UnitedHealth Group shares tumbled early Friday on a report that the U.S. Department of Justice has started an investigation into the health care giant’s Medicare billing practices

Hi, it’s John in New York. I’ve spent years following a story about how whistleblowers alleged systematic fraud at private Medicare Advantage plans. A reported investigation at one of the biggest companies in that business jolted investors last week.

Sen. Chuck Grassley (R-Iowa) has given UnitedHealth Group two weeks to explain its method for documenting Medicare Advantage enrollees' diagnoses.

By Brendan Pierson (Reuters) -A court-appointed special master has found that U.S. authorities do not have evidence to support their billion-dollar fraud case accusing UnitedHealth Group of keeping overpayments from the government for patients on its Medicare insurance plans.