AIM Healthcare Services Inc., which has become a national leader in its field of payment auditing from its Franklin headquarters while keeping a low corporate profile locally, has sold out to a unit of insurer UnitedHealth Group.

Ingenix, UnitedHealth's information technology consulting arm based in Eden Prairie, Minn., announced this morning that it is purchasing AIM in an all cash deal. The price was not disclosed, but sources contacted by NashvillePost.com have said it was about $430 million.

AIM, founded in 1990, is in the business of detecting and managing inaccurate medical bills. It makes its money by helping payors, like the government and insurers, as well as providers, like doctors and hospitals, to prevent errors as they generate invoices and payments in the healthcare sector — a flow of money so huge that it accounts for over one sixth of the entire American economy.

Today's announcement cites recent research by The Lewin Group suggesting that claims inefficiencies cost the U.S. health care system more than $150 billion a year.

AIM has given out little information over the years about the scale of its business. But it is known to have more than 4,000 customers across all 50 states, and it has long been regarded as the largest player in its niche of the healthcare industry. In the course of a hard-fought legal battle between AIM and a rival local firm that was resolved in 2006, it was revealed that AIM recovered overpayments of more than $1 billion in 2004.

"AIM will contribute to existing Ingenix solutions for preventing, detecting and correcting errors throughout the claims life-cycle," today's announcement said. "AIM’s portfolio will also bolster Ingenix’s coordination of benefits capabilities, particularly for federal and state government payer clients."

AIM's top officers are Chairman Preston Ingram, a prominent Williamson County investor; CEO Jim Sohr; Carl Haley, vice president; and Burt Nowers, chief financial officer.