Filing prior art

After a patent application is made available to the public, anyone can raise questions about the patentability of the invention or one of its claims by filing prior art.

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What is prior art?

Prior art consists of all information/documentation that has been disclosed with the public about an invention before the filing date of the patent in question. Patentability (novelty, utility, and inventiveness) must be assessed during the examination process in view of the prior art as it could impact the eligibility for a patent.

Any prior art filed is considered by the examiner only after examination has been requested. Information contained in a filing of prior art is taken into account and will be used during examination if it is found to be pertinent by the examiner.


You are aware of a Canadian application to patent an electric door lock. But, you have evidence of an earlier electric door lock, either yours or another inventor's, which is already known, publicly described or demonstrated. The public disclosure of the door lock constitutes prior art and it does not need to be in existence nor be available on the market to be considered so. You may inform the Canadian Intellectual Property Office (CIPO) that such a door lock was previously known, before the current application was made.

Filing prior art

Under Section 34.1 of the Patent Act, any third party can file prior art with CIPO, explaining why they believe a claimed invention is not new or inventive. Prior art filed with CIPO becomes a part of the application file and can be accessed by the public.

When filing prior art, the submission will be acknowledged but no further information will be made available, such as resulting action taken or discussion with an examiner to discuss the prosecution of the application. However, access to the prosecution file of the application at the time the file is opened to public inspection is made available and can be followed on the Canadian Patents Database. The applicant is notified that a submission of prior art has been made.

In the event the application is of Patent Cooperation Treaty origin and has not yet entered the national phase in Canada, CIPO will retain the third party submission until the date for late national entry in Canada has passed.

Reasons to file third party prior art

Improving patent quality and increasing the quality and efficiency in the examination process are key goals of IP offices around the world. IP offices recognize that the public can play an important role in ensuring all potentially relevant prior art is considered while a patent application is being examined.

Prior art, submitted by a third party, allows informed individuals to provide relevant information to patent examiners potentially blocking competitors from obtaining a patent for inventions that were previously disclosed. It also becomes part of the laid-open application file made available to the public. Filings of prior art requesting confidentiality will be returned to the sender and will not be considered by the examiner.

How to file third party prior art

Prior art is filed in writing to:

Commissioner of Patents
Place du Portage, Phase I, Room 403B
50 Victoria Street
Gatineau, Quebec
K1A 0C9

In your correspondence, indicate:

  • the relevant patent application number
  • the prior art
  • why the prior art is pertinent

Additional reading

Refer to CIPO's Manual of Patent Office Practice, Chapter 18 18.01.