Can a patent have 2 CPC classes to it? Is it strictly 1?

Let's say the patent is classified in order for it to be given to a specific unit to study it, does the patent go only to one unit? To clarify, see patent classes as a tree with branches getting more detailed as you go deep. Does a patent get sorted into only ONE last branch?

Note: the CPC is the COOPERATIVE PATENT CLASSIFICATION system jointly developed by the USPTO and the EPO for putting patents into categories by the claimed subject matter. The traditional US classification is the U.S. Patent Classification System (USPC).

2 Answers 2


I believe George White's answer solves your question. Notwithstanding, please note that how patent documents are classified in terms of IPC/CPC classes is different in each patent office. At the EPO, the so-called Receiving Section attempts to establish what is the technical field of the invention so that a Search Division (actual examiners) draw up a search report. If the Receiving Section gets this wrong, the examiner that receives the file can move it to another unit. The Search Division then assigns the IPC/CPC classes based on the contents of the application, and yes, a same patent application can be classified in multiple IPC/CPC depending on what is disclosed in the application, not only what is claimed. The examiner is supposed to assign the most accurate subgroups, but sometimes it is not easy to establish which ones those are and they get classified at group level for example. You can find some more information about this process here.

Some patent offices still use IPC, so in some patent documents you will not find any USPC or CPC code.

  • What you mean is, patents may only be group-level coded if unsure of subgroup so they go deep enough until they are unsure. Is another case (and it is not common but I am just hypothesizing) of patents belonging to biology and electrical topics for example, be split early in the CPC and actually reside under 2 different codes? So my question is, is it possible for a patent to exist in 2 places in the CPC branches?
    – Solving Py
    Aug 1, 2020 at 13:57
  • @SolvingPy They can be at group level if unsure as you mention or if the examiner does not want to spend much time finding the most appropriate subgroups (if any). And yes, a same patent document can be classified in two or more completely different CPC groups/subgroups. Advanced patent databases retrieve the CPC/IPC of all members within a patent family too, so your filtering can benefit from that when e.g. the Chinese examiner classifies the Chinese patent application in a particular CPC and the US examiner classifies the US patent application in another CPC. Aug 2, 2020 at 14:32
  • @SolvingPy As a sidenote, the EPO has staff devoted to reclassification of patent documents. Usually this staff is to add or modify the CPC codes of patent documents when new CPC subgroups are created, therefore you can find old documents being classified in very recent CPC codes thanks to this staff. Third parties benefit from these reclassifications, but what matters most is that the patent system becomes better as it is more likely that examiners will find relevant disclosures for each invention using the patent classification system. Aug 2, 2020 at 14:38
  • @SolvingPy A couple of examples found in a quick search I have made, each with two or three very different subgroups: one and two Aug 2, 2020 at 15:09

Nothing for you to worry about.

The classification systems exist for two reasons. It is how the examining corp is organized. Examiners become experts in one or more related classes. Your examiner will be in an "art unit" that examines things from one or more related classes. Although you have the option to suggest a class/subclass when applying, the primary class is actually chosen by a semi-automated process based on the text of claim 1. Your application is then steered to a particular art unit. For the sophisticated, there are strategic attempts to get it to one unit vs another unit.

It is also a way to search for patents. Before there were computers allowing text searching they need to be organized in some way. We still use it in professional searching - it often finds things that a text search does not.


The IPC (international classification system) is not as fine grained as either the US or CPC and is not particularly relevant to the examining process.

In the USPTO each appliation is assigned to an art unit within a technology center. Each art unit examines a handful of closely related class/subclases. The supervising examiner (SPE) of that art unit assigns a single specific examiner to the application. The classification is based on the claimed subject matter.

If some claims would be in a quite different class/subclass from the others the examiner will issue a restriction requirement and the applicant is forced to chose which set of claims will be examined in the course of this application.

  • That does not answer my question. What I want to say is, can a patent be filed under 2 codes? For example if patent is found under BXXXXX/00, and it talks about 2 fields maybe, is there ANY case it can be under another code (like even if 99% of patents are under 1, any rare cases will do)
    – Solving Py
    Jul 27, 2020 at 12:10
  • If you look at the face of almost any patent you will see many class/subclasses listed. The first one is bolded. an example US7076613B2 has 13 classes listed U.S. Cl. ....................... 711/141; 711/118; 711/121: 711/124; 711/142; 711/143: 711/144; 711/128; 711/137; 711/147; 711/205: 711/206
    – George White
    Jul 27, 2020 at 17:10
  • You do not file it under a "code". It is assigned to an examiner in an art unit that is appropriate for the content of the application. How that is determined is by classification. If you explained your actual issue you might get an answer that you found useful.
    – George White
    Jul 27, 2020 at 17:14
  • it has only one International cl, which is what I am looking at. I am sorry i did not explicitly get right how it works. I also updated my question for an analogy
    – Solving Py
    Jul 27, 2020 at 21:42

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