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Date Published

The CPC uses the hierarchical structure of the IPC, from sections down to subgroups (see Structure of the IPC). However, the CPC has many more subdivisions or subgroups than the IPC and CPC indexing codes are conventionally called 2000 series.

The CPC is divided into 9 sections A-H and Y.


Main trunk

The main trunk contains sections A-H, which correspond to the eight sections of the IPC. The main trunk is for classifying both invention and additional information (see Invention information and additional information).


2000 series

The CPC also contains the 2000 series with the subclass symbol followed by a four-digit number beginning with '2'. The 2000 series symbols can be used only for allocation of "additional information”.

References to the indexing codes of the 2000 series are not allowed, as indexing schemes are secondary to the CPC main trunk.

There are two main kinds of 2000 series: further breakdown indexing codes and orthogonal indexing codes.


Further Breakdown Indexing Codes

Breakdown indexing codes are dependent on a hierarchically superior main-trunk group and interspersed within CPC main-trunk symbols.

The symbol of these indexing codes begins with ‘20’, followed by a two-digit number of the main group. If the number of the main group is a single digit, a zero is added to the front of the single digit, for example ‘6’ becomes ‘06’ and the 2000 series numbering is ‘2006’. These symbols are also highlighted in red to distinguish them from the main trunk.

Example: Further breakdown code G08B 2001/085

It is the EPO and USPTO policy to progressively reduce the number of (further) breakdown indexing codes in the CPC Scheme (in favour of “main-trunk” symbols) and not to promote the creation of new breakdown indexing codes.


Orthogonal Indexing Codes

The orthogonal indexing codes are independent from a hierarchically superior main trunk group (not interspersed with the main trunk) and usually relate to multiple groups of the subclass.

The symbol of these indexing codes begins with ‘2’, followed by another digit other than ‘0’ to distinguish this group from the Further Breakdown Indexing Codes.

They usually relate to multiple groups of the subclass in question, and hence they are called “orthogonal” in the sense that they offer further dimensions to the classification: they are “orthogonal” to the classification line of the main trunk.

In the example below, orthogonal indexing code B65D2101/00 and its subgroups relate to multiple main trunk groups under subclass B65D, including B65D1/00 up to B65D90/00. Similarly, another orthogonal indexing code B65D2590/00 and its subgroups relate to multiple main trunk groups under subclass B65D.

IPC indexing codes

IPC indexing schemes are also copied (if appropriate) into CPC.

For the sake of consistency with the numbering used for any CPC indexing code (2000+), IPC indexing codes carry a 2 in front of the original IPC number.


IPCF21Y 101/00Point-like light sources
CPCF21Y 2101/00Point-like light sources



Section Y

Section Y is the ninth section of the CPC. Subclasses under Y02 and T04 cater for the “tagging” of emerging technologies, which span many sections of the CPC, and subclasses under Y10 are for USPTO cross reference art.

Section Y comprises three parts:

  • Y02 - Climate change inventions: for example, energy efficient technologies (lighting, heating, air conditioning, etc.), wastewater treatment, greenhouse gases
  • Y04 - Computer and Communication technology impinging on other technologies: systems integrating technologies related to power network operation, communication or information technologies for improving electrical power generation, transmission, distribution, management or usage, i.e. smart grids
  • Y10 - United States Patent Classification (USPC) cross reference art: a temporary location for old USPC. These symbols will be included in the main trunk where possible, otherwise will be removed by the end of 2016


Note that there are no 2000 series symbols in the Y section.

The allocation of Y symbols should not be done manually by classifiers during the normal process of classification. The “tagging” occurs as relevant documents are captured automatically by search strategies (developed by EPO specialists) and given relevant symbols from the Y-section.


IPC groups not used in the CPC

IPC groups should always be replicated in the CPC, as the IPC is the “backbone” of the CPC.

Yet in some exceptional cases, in the past (pre-CPC age), “deviations from the IPC” were allowed in some areas.

The general policy of CPC is not to allow such deviations any longer. In addition, existing deviations should progressively, and insofar as possible, be eliminated, in order to progressively reduce the differences between the two systems.

When IPC groups are not used in the CPC, a warning is placed after the subclass title to inform the users of the deviation from the IPC practice, and to indicate where the corresponding subject matter is classified in CPC.



Amended Reasons

Amended Reason Date Amended
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