This month CMS mailed its first Medicare comparative billing reports (CBRs) to as many as 5,000 physical therapists, comparing the providers' individual billing practices for specific procedures and services with those of their peer group. The initial CBRs are based on 2009 Medicare claims data from outpatient physical therapy services provided by independent physical therapists. Physical therapists were selected for the program based on identified vulnerabilities in their billing procedures involving the use of the KX modifier (which indicates that a service was medically necessary and justified by medical records, that the physical therapy financial limitation cap was met, and that a patient's condition requires further treatment). The CBR program ultimately is designed to reduce improper payments and educate providers on Medicare billing requirements.