State agrees to investigate HMO billings.(United HealthCare of Florida)

ORLANDO - State insurance officials are investigating the billing practices of one of Florida's largest managed care companies.

At issue is whether United HealthCare of Florida is underpaying some doctors, a complaint made by the 17,000-member Florida Medical Association, the state's largest physicians' organization.

The dispute centers on billing codes doctors use to file insurance claims.

Each of the codes signifies a different level of care or type of treatment. For example, one code represents an office visit that involves a good deal of the doctor's time, such as a patient with a chronic illness. Another code reflects a brief office visit for a …