Revenue Center HCFA Common Procedure Coding System

The Health Care Common Procedure Coding System (HCPCS) is a collection of codes that represent procedures, supplies, products and services which may be provided to Medicare beneficiaries and to individuals enrolled in private health insurance programs. The codes are divided into three levels, or groups as described below:
Level I: Codes and descriptors copyrighted by the American Medical Association's Current Procedural Terminology, Fourth Edition (CPT-4).  These are 5 position numeric codes representing physician and nonphysician services.
*Note: CPT-4 codes including both long and short descriptions shall be used in accordance with the CMS/AMA agreement.  Any other use violates the AMA copyright.
Level II: Includes codes and descriptors copyrighted by the American Dental Association's Current Dental Terminology, Fifth Edition (CDT-5).  These are 5 position alpha-numeric codes comprising the D series.  All other level II codes and descriptors are approved and maintained jointly by the alpha-numeric editorial panel (consisting of CMS, the Health Insurance Association of America, and the Blue Cross and Blue Shield Association).  These are 5 position alpha-numeric codes representing primarily items and nonphysician services that are not represented in the level I codes.
Level III: Codes and descriptors developed by Medicare carriers for use at the local (carrier) level. These are 5 position alpha-numeric codes in the W, X, Y or Z series representing physician and nonphysician services that are not represented in the level I or level II codes.
HCPCS - General Information (CMS Website)