Re-examination is the only post grant procedure available in the Canadian Patent Office that allows a third party to challenge the validity of a Canadian patent. From its inception in October 1989, up to September 2013, there have been only 79 re-examination requests in Canada. This figure contrasts sharply to the situation in the U.S., where post grant proceedings in the U.S. Patent Office are much more frequent. This article provides some background on the re-examination process in Canada, discusses its limitations and also compares and contrasts re-examination to the other main post-grant procedure for attacking an issued patent in Canada, namely patent impeachment.


Re-examination is provided for in sections 48.1-48.5 of Canada’s Patent Act (“the Act”).

Pursuant to section 48.1 of the Act, any person may request a re-examination of any claim in an issued patent by filing prior art consisting of patents, published applications, and printed publications with the Commissioner of Patents. The request for re-examination must also include written submissions setting forth the pertinency of the prior art and the manner of applying the prior art to the claims in issue.

A request for re-examination may be made at any time after a patent has issued, until the expiration date of the patent. Once the request is made, the Patent Office will forward a copy of the request to the patentee. A re-examination board is then established and makes a determination as to whether a substantial new question of patentability affecting any claim of the patent in issue has been raised in the request. This determination is made within 3 months.

Where it is determined that a substantial new question has not been raised, the board will notify the requesting party and its decision in this regard is final for all purposes and is not subject to appeal or review by any court. Of the 79 re-examination requests made in Canada, no substantial new question of patentability was found in 19 cases.

Where, however, it is determined that a substantial new question has been raised in the request, the patentee is notified and has 3 months to file a reply to the notice setting out submissions on the new question of patentability.

In response to the notification, the patentee may suggest amendments to the claims at issue, submit new claims or cancel certain claims, so long as the scope of the claims is not broadened as compared to the claims of the original patent.

Upon receipt of a reply, or in the absence of a reply from the patentee, the re-examination board causes the re-examination process to be initiated. The board must render a decision as to patentability of the claims at issue within 12 months from the date that the board commenced the re-examination process. The board’s decision may be appealed to the Federal Court, but only by the patentee.

If the board decides to cancel one or more of the claims, the patent is deemed to have been issued from its date of grant, but in its corrected form. If all the claims are cancelled, the patent is deemed to never have been issued. If a new claim is incorporated, or a claim is amended, the new or amended claim is effective from the date of the issued re-examination certificate and will remain valid until the expiry of the patent term.

In approximately two thirds of all re-examination board decisions to date, at least one claim at issue was cancelled or amended.


Pursuant to section 60 of the Act, proceedings for impeachment may be brought against any issued patent before the Federal Court and may be instituted by any interested person. “Interested person” has been interpreted broadly by the Court, and can include, for example, a party which may expect to have the patent asserted against it (e.g. in view of the manufacture or sale of a product in Canada which may arguably fall within the scope of the patent). Receipt of a cease and desist letter from the patentee is typically not a pre-requisite to commencing such a proceeding.

In an impeachment proceeding, the burden is on the interested person to prove that the patent or one or more of the patent’s claims are invalid or void. An impeachment proceeding can raise any ground of invalidity, including obviousness and novelty attacks based on prior art and technical grounds pertaining to certain intrinsic defects in the patent itself.

An impeachment proceeding is typically brought by way of action. An action in the Federal Court includes the following basic steps:

  1. Pleadings: In the pleadings, the parties set out the relief sought, and particulars as to allegations made (including all bases for invalidity alleged). It can also be expected that the patentee would counterclaim for infringement.
  2. Documentary Discovery: Each party is required to serve a list of relevant documents. Copies of non-privileged documents are exchanged.
  3. Oral Discovery: Usually a party has the opportunity to examine a single representative of an adverse party. Inventors of the patent in issue may also be examined.
  4. Pre-Trial Steps: Pre-trial steps may include a mediation or other court-directed settlement meeting, exchange of expert reports, and setting of a trial date.
  5. Trial: A trial in the Federal Court is conducted before a judge who decides all legal and factual issues.

Typically, an impeachment action will require 2-3 years to complete. However, if pursued aggressively, it is possible to have the action completed within two years. A decision of the Federal Court may be appealed to the Federal Court of Appeal by either party.

Re-examination versus Impeachment

Re-examination is a relatively quick and inexpensive procedure for third parties to challenge the validity of a patent. However, it is subject to important limitations, which may account (in part) for the relatively few re-examinations in Canada to date. Importantly, once the process is initiated, a third party does not have the opportunity to make further submissions with respect to the patentability of the existing claims, or any amended or new claims. Moreover, as noted above, only the patentee has a right of appeal, and there is no opportunity to appeal a finding of the re-examination board that no substantial new question affecting patentability of any claim has been raised by the request for re-examination. Further, only patents, applications and printed publications may be submitted for review on re-examination. Therefore, prior uses and sales, and other important validity issues such as utility and sufficiency, cannot be raised during a re-examination.

For these reasons, in important cases, it may be preferable for a third party to proceed by way of a patent impeachment action, in which all invalidity issues may be raised, discovery may be pursued, evidence (including expert evidence) may be adduced, and detailed submissions may be made to a judge for consideration. Weighing against these advantages are the cost and timeline. Because the impeachment action is a contested proceeding before the Federal Court, and may also involve a counter-claim for infringement brought by the patentee, the costs associated with an impeachment action are significantly higher than those associated with a re-examination proceeding and the timeline may be significantly longer.


Whether re-examination or a patent impeachment action is commenced depends largely on an assessment of issues such as cost, timing, and the relative importance of initiating an attack on an issued patent. Experienced patent counsel can help determine which procedure might be most advantageous in any given situation. Overall, the narrow scope of re-examination in Canada is often a deciding factor in choosing between these two alternatives.