Amid the U.S. Department of Justice’s (DOJ) legal battle with UnitedHealth Group (NYSE: UHG) regarding the planned purchase of Amedisys (Nasdaq: AMED), the company is also now reportedly facing an investigation for a different matter.

The DOJ is currently pursuing a civil fraud investigation focused on the company’s practices for recording diagnoses that activate extra payments to its Medicare Advantage (MA) plans, The Wall Street Journal reported Friday.

“The government regularly reviews all MA plans to ensure compliance and we consistently perform at the industry’s highest levels on those reviews,” UnitedHealth Group wrote in a press statement. “We are not aware of the ‘launch’ of any ‘new’ activity as reported by the Journal. We are aware, however, that the Journal has engaged in a year-long campaign to defend a legacy system that rewards volume over keeping patients healthy and addressing their underlying conditions. Any suggestion that our practices are fraudulent is outrageous and false.”

Overall, UnitedHealth Group is one of the largest companies in the country and has an array of associated business lines. Optum – UnitedHealth Group’s provider services arm – owns home-based care giant LHC Group.

Plus, UnitedHealth Group’s UnitedHealthcare is the nation’s largest Medicare Advantage provider. The company accounted for 29% of all MA enrollment in 2024. Last year, there were 32.8 million individuals enrolled in a MA plan in total, according to data from KFF.

Reporting conducted by the Wall Street Journal found that Medicare compensated UnitedHealth billions of dollars for “questionable diagnoses.” Reports also found that the company included diagnoses to patients’ records for conditions that were never treated by doctors, which activated an additional $8.7 billion in federal compensation in 2021. One of the sources for the untreated diagnoses came from the company’s HouseCalls unit.

Historically, MA coding practices are a constant source of friction between the industry and regulators. In the past, DOJ civil lawsuits related to MA coding practices have been launched against Cigna Group (NYSE: CI), according to a Stephens note released Friday.

“The investigation’s initial launch seems to overlap with the Biden DOJ,” Scott Fidel, the managing director at the investment banking company Stephens, wrote. “The question is how vigorously Trump’s DOJ will continue to pursue the case. However, the subject of fraud/waste/abuse is a prime area of DOGE’s [Department of Government Efficiency] interest.”

Following reports of the DOJ investigation, UnitedHealth Group’s shares plunged almost 9% today.