What is the CPC classification system and how is it structured?

This page is an FAQ based on guidance from the Manual of Patent Examining Procedure. It is provided as guidance, with links to the ground truth sources. This is information only: it is not legal advice.

The Cooperative Patent Classification (CPC) system is a hierarchical arrangement of subject matter used for organizing and classifying patent documents. According to MPEP 905.01, the CPC structure consists of:

• Sections: The highest level, designated by capital letters A through H and Y.
• Classes: Subdivisions of sections, identified by a section letter followed by a two-digit number.
• Subclasses: Further subdivisions, adding a letter to the class symbol.
• Groups: Main groups and subgroups within subclasses.

The MPEP states: “Each part of this hierarchical structure is identified by classification symbols. Specifics about each element of the classification symbol are described below.”