Reasonable charges are developed nationally and then adjusted locally by each VA medical center based on their Geographical Area Adjustment Factor (GAAF). Billing for inpatient facilities and skilled nursing facilities are on a per diem basis. For inpatient facility charges, the per diem charges vary by the treated condition as classified by Medicare Severity Diagnosis Related Groups (MS-DRG) codes. Billing for outpatient facility and provider charges vary by procedure performed as classified by current procedural terminology (CPT) codes and Healthcare Common Procedure Coding System (HCPCS) Level II codes. Data for calculating actual charge amounts are published in a notice within the Federal Register or can be viewed on the VHA OCC website."