Do You Think That Patent Is Invalid?

You or your client may come across a patent or patent application and be aware of prior art or have other reasons to believe it is invalid. The patent may have shown up in a patent search, such as a freedom to operate search or be listed in a demand letter sent by the competitor.

Depending on the situation, the competitive situation, and the budget, there are several ways to challenge the validity of a Canadian patent application or issued patent. I recommend involving a patent agent and/or patent lawyer to assist with determining which, if any, option is best for a particular situation.

File a protest against a patent application

If the patent application is still pending at the Canadian Patent Office, anyone can file a ‘protest’ with the patent office against the patent application. All patent applications are published within 18 months of being filed and a copy of the application and the full file history can be obtained from the Canadian Patent Office.

Protests can either be copies of prior art with an explanation of its applicability (s.34.1 of the Patent Act) or simply a written communication intending to protest the granting of a patent (s. 10 of the Patent Rules).

The Canadian Patent Office will acknowledge receipt of the protest but does not provide any updates as to the effect of the protest on the patent application. The examiner at the Canadian Patent Office reviewing the application may, or may not, act on the material in the protest, such as by incorporating the prior art into an objection sent to the patent applicant. It may be worth monitoring a patent application after a protest is filed to see the result of the protest on the application.

If fully incorporated by the examiner into a rejection, the protests may result in the patent application being rejected, or the applicant may be able to amend the claims to overcome the prior art and obtain a stronger patent than they would have without the protest. It is possible to file multiple protests against the same application if the first protest is not successful.

Request re-examination of an issued patent

Once a patent has issued, it is possible to file a request for re-examination (s. 48.1 of the Patent Act) of a granted patent. Re-examination may be requested by anyone, including the patentee, at any time after a patent is issued, but only on the basis of prior art, namely patents, patent applications and printed publications. A re-examination cannot be based on prior public disclosures that are not in written documents or other attacks on validity such as utility or sufficiency. The request must identify the pertinence of the prior art and the manner of applying the prior art to the claims.

In response to a request for re-examination, the patent office forms a re-examination board which considers whether the re-examination request raises “a substantial new question of patentability”. If board decides it does, the patentee is notified and the patentee can then respond, including with proposed claim amendments to address the prior art. The board issues a certificate either cancelling claims, confirming claims or incorporating claim amendments proposed by the patentee. The entire process must be completed within one year.

The patentee can appeal a re-examination decision to the Federal Court. If someone other than the patentee requests re-examination, there is no option to participate in the process or to appeal to the Federal Court, which limits the attractiveness of this procedure for non-patentees. Less than a hundred re-examination requests have been made in the 25 years since this procedure was introduced.

Re-examinations are significantly more popular in the United States which has both inter parte and ex parte procedures and has more recently added post grant review and the covered business method patents review, all for reviewing granted patents within the patent office. Hundreds of requests for re-examination are filed each year in the United States.

Impeachment in the Federal Court

Another option for challenging the validity of a patent is to bring an impeachment action in the Federal Court under s. 60 of the Patent Act. The action may be brought by any “interested person” as defined in the Patent Act and the patentee is named as the defendant. As noted in one of my earlier columns, an impeachment action must be brought in the Federal Court, not one of the provincial courts.

Unlike the other procedures already discussed, an unsuccessful plaintiff in an impeachment action may be required to pay a portion of the legal costs to the patentee. Section 60(3) of the Patent Act requires that security for costs be posted before the Statement of Claim is issued.

Any ground of patent invalidity may be alleged in the impeachment proceeding and there is full documentary and oral discovery and other pre-trial steps. The trial in an impeachment action involves live witnesses before a Federal Court judge.

The patentee defendant in an impeachment action may counterclaim for patent infringement which can increase the complexity of the proceeding and the risks for the plaintiff. The cost for an impeachment action is significantly more than either of the other options and typically takes longer, usually 2 to 3 years.


When considering a patent and these options, it is important to also consider the costs, likely result, implications for patent positions in other jurisdictions and the possible counter-measures the patentee may take in response. In many cases, simply waiting to see if a patentee asserts the patent may be the preferred option rather than proactively initiating a re-examination or impeachment proceeding.


  1. A very good summary by Alan here. As an aside anyone interested in Canadian IP law should definitely be on Alan’s mailing list found at

    From my own experience challenging patent applications before they issue in Canada and the US has led to successful outcomes for clients in many cases, but there is definitely costs and risks involved, which make it suitable only in some situations. An active review of competitors portfolios assists in identifying which applications, if any, are worth challenging.

    If anyone is interested in more detail on the approach to challenging a pending US patent application that Alan mentioned there is more detail in a paper I co-wrote :
    Third-party submissions for patent applications pending before the USPTO
    Journal of Intellectual Property Law & Practice 2013; doi: 10.1093/jiplp/jpt160