MPEP § 905.01 — Classification Scheme for CPC (Annotated Rules)

This page consolidates and annotates all enforceable requirements under MPEP § 905.01, including statutory authority, regulatory rules, examiner guidance, and practice notes. It is provided as guidance, with links to the ground truth sources. This is information only, it is not legal advice.

Classification Scheme for CPC

This section addresses Classification Scheme for CPC.

Key Rules

Definitions & Scope (5)

MPEP GuidanceInformativeAlways

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Subject Matter Arranged Hierarchically

Note:

The CPC classification system organizes subject matter into a hierarchical structure, starting from sections and subdividing into classes, subclasses, and groups.

The CPC classification system arranges subject matter into hierarchical arrays.
(A) The highest array or level is the Section.
(B) Each section is subdivided into Classes.
(C) Each class is subdivided into one or more subclasses.
(D) Each subclass is broken down into Groups (main groups and subgroups).

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MPEP GuidanceInformativeAlways

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Highest Level of CPC Classification Is Section

Note:

The highest level in the CPC classification system is designated as a Section.

The CPC classification system arranges subject matter into hierarchical arrays. (A) The highest array or level is the Section.

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MPEP GuidanceInformativeAlways

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Each Section Divided Into Classes

Note:

The CPC classification system divides each section into classes to organize subject matter hierarchically.

The CPC classification system arranges subject matter into hierarchical arrays.
…
(B) Each section is subdivided into Classes.

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MPEP GuidanceInformativeAlways

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Classes Must Be Subdivided into Subclasses

Note:

Each class in the CPC classification system must be subdivided into one or more subclasses to organize subject matter hierarchically.

The CPC classification system arranges subject matter into hierarchical arrays.
…
(C) Each class is subdivided into one or more subclasses.

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MPEP GuidanceInformativeAlways

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Each Subclass Is Divided Into Groups

Note:

The CPC classification system requires each subclass to be divided into main groups and subgroups.

The CPC classification system arranges subject matter into hierarchical arrays.
…
(D) Each subclass is broken down into Groups (main groups and subgroups).

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Source Text from USPTO’s MPEP

This is an exact copy of the MPEP from the USPTO. It is here for your reference to see the section in context.

905.01 Classification Scheme for CPC [R-07.2015]

The CPC classification system arranges subject matter into hierarchical arrays.

(A) The highest array or level is the Section.
(B) Each section is subdivided into Classes.
(C) Each class is subdivided into one or more subclasses.
(D) Each subclass is broken down into Groups (main groups and subgroups).

Each part of this hierarchical structure is identified by classification symbols. Specifics about each element of the classification symbol are described below.

(A) Section Symbol – Each section is designated by one of the capital letters A through H and has an associated section title. There are nine sections, eight of which correlate to the sections of the International Patent Classification (IPC). The ninth section is used for classifying documents covering subject matter pertaining to a plurality of the sections. The table below shows the sections with their associated CPC and IPC section titles.


Letter Designation	CPC Section	IPC Section
A	Human Necessities	Human Necessities
B	Performing Operations; Transporting	Performing Operations; Transporting
C	Chemistry; Metallurgy	Chemistry; Metallurgy
D	Textiles; Paper	Textiles; Paper
E	Fixed Construction	Fixed Construction
F	Mechanical Engineering; Lighting; Heating; Weapons; Blasting Engines or Pumps	Mechanical Engineering; Lighting; Heating; Weapons; Blasting Engines or Pumps
G	Physics	Physics
H	Electricity	Electricity
Y	General Tagging of New Technological Developments; General Tagging of Cross-over technologies spanning over several sections of the IPC; technical subjects covered by former USPC cross reference art collections and digest

(B) Class Symbol – Each class symbol consists of the section symbol followed by a 2 digit number (e.g., C07). Each class symbol is associated with a title.

(C) Subclass Symbol – Each subclass symbol consists of the class symbol followed by a letter (e.g., C07D). Each subclass symbol is associated with a title.

(D) Main Group Symbol – Each main group symbol consists of the subclass symbol followed by a one- to four- digit number, the oblique stroke, and the number 00 (e.g. C07D 203/00). Each main group number is associated with a main group title which precisely defines a field of subject matter within the scope of its subclass and a definition.

(E) Subgroup Symbol – Each subgroup symbol consists of the main group symbol, but the number “00” in the main group symbol is replaced with an alternative number of up to six digits (e.g. C07D 203/02). Each subgroup symbol is associated with a title and definition.

Example:

CPC Symbols C07D 203/00 or C07D 203/02

BlueIron Last Updated: 2025-12-31