Patent Re-Examination in Canada

The Canadian Patent Office has a procedure for the “re-examination” of a granted patent. However, this procedure is rarely used in Canada for several reasons. Less than half a dozen re-examinations are filed each year.

Anyone, including the owner of the patent may request re-examination on the basis of prior art, namely patents, patent applications and printed publications (see s. 48.1 of the Patent Act). The patent office forms a panel that determines whether the request raises “a substantial new question of patentability”.

If so, the patentee is notified and the patentee can respond to the request, including providing argument and proposed claim amendments to address the prior art. The board then issues a certificate either cancelling claims, confirming claims or incorporating the claim amendments proposed by the patentee. The entire process following the patentee’s response must be completed within one year. There is an appeal option available to the patentee to the Federal Court.

For someone concerned about a patent, the re-examination procedure has some disadvantages. These include, being limited to relying only on “patents, applications for patents open to public inspection and printed publications” as prior art. There is no opportunity to rely on prior disclosures (i.e. public prior art uses) or expert evidence to explain the technology and the common general knowledge.

Secondly, once the request is filed, the requester has no role in the procedure. The requester does not get an opportunity to rebut the patentee’s submissions or address the patentee’s proposed claim amendments. Also, the requester does not have standing to appeal a decision by the re-examination board to confirm the claims.

Thirdly, because the patentee can submit claim amendments, the patentee can make their patent ‘stronger’ by narrowing the claims to address prior art. This contrasts with validity challenges in the Federal Court, either by way of impeachment or in defence to infringement, that do not allow claim amendments.

As a result of these factors, re-examinations in Canada are rare. My analysis suggests that typically less than half a dozen re-examinations are filed each year in Canada. The most recently request for re-examination that I have located is against CA3,168,669 filed by a third party in May 2025.

Some recent court cases have also identified disadvantages to pursuing re-examination.

In Zacon Limited v. Provincial Doors Inc., 2025 ONSC 2954, the plaintiff patentee sought to struck out invalidity defences on the basis that an earlier re-examination request using the same prior art had been unsuccessful. While the motion to strike was dismissed, the defendant had to face the risk that its defences would be struck and it would be limited in its invalidity challenges. The court held that the “same question” had not been determined earlier by the re-examination board, namely “patentability” as compared to the question of “validity” to be determined by the court.

Some earlier court decisions have also concluded that re-examination and court proceedings are different. In Pfizer Canada ULC v. Uniqure Biopharma B.V.. 2023 FC 629, the court did not stay litigation while a re-examination was pending. The court concluded (at paragraph 42) that “The scheme of the Patent Act suggests that re‑examination and impeachment are separate and distinct paths that can proceed in parallel.”

On the other hand when asked to stay re-examinations the courts seem open to arguments that the more comprehensive court proceeding be permitted to go ahead, while the re-examination is stayed – even though both processes address the same issues of obviousness and anticipation.

In Teva Canada Innovation v. Pharmascience Inc., 2021 FC 367, the court stayed a pending re-examination to avoid the risk of “inconsistent decisions surrounding patent validity”. In this case, the court determined that “it appears undisputed that the Re-examination Proceeding and the Federal Court litigation in this matter are, at least in part, duplicative” and addressed the “the same issues” as the court proceeding.

Similarly an older proceeding, Prenbec Equipment Inc. v. Timberblade Inc., 2010 FC 23, the court granted a stay of a re-examination on the basis that the parallel court proceedings where more comprehensive and could deal with credibility issues surrounding a key piece of prior art, unlike the re-examination board. Also in Camso Inc. v. Soucy International Inc., 2016 FC 1116, a stay was granted on the basis that the, “legal issues in the request for re-examination are the same as the challenges against the validity of the 562 patent with regard to lack of novelty and obviousness” and that the court proceeding has “a broader remedy that allows more substantial evidence to be received that should favour the interests of justice.”

The interplay between re-examination procedures before the patent office and validity arguments in court have played out in other jurisdictions as well. In the United States, it has been common for defendants in litigation to bring Inter Parte Reviews (IPRs). In some districts, the infringement cases are stayed while the IPRs are resolved, providing significant benefit to defendants, particularly because historically IPRs have resulted in many patents being found invalid. However, estoppel typically applies to prior art that a party raised in the IPRs if included in a subsequent infringement proceeding, although not necessarily prior disclosures or systems (rather than patents and printed materials) – see for example Ingenico Inc. v. IOENGINE, LLC, No. 23-1367 (Fed. Cir. May 7, 2025). Changing rules about whether to stay district court litigation, as well as changes that make it more difficult to institute IPRs likely make IPRs less appealing to defendants.

The limitations of the re-examination procedure in Canada, and the interplay with more comprehensive invalidity issues in court proceedings means that in spite of its lower cost and faster disposition, re-examinations are rare and typically not a recommended strategy for a potential defendant facing allegations of patent infringement.