Canada: Double-Patenting: The Canadian Perspective For U.S. Practitioners

Since the Supreme Court of Canada decision in Whirlpool Corp. v. Camco Inc., 2000 SCC 67, double-patenting has become a common challenge to patent validity in Canada. The Canadian double-patenting doctrine is similar to the U.S. double-patenting doctrine, but subtle differences between the two can potentially lead to a fatal double-patenting issue for a Canadian patent that would otherwise be easily resolved for its U.S. counterpart under U.S. practice. Similarities and differences between the Canadian and U.S. double-patenting doctrines are discussed in this article and some strategies are identified for potentially mitigating double-patenting risks in Canada.

Contrast between Canadian and U.S. double-patenting laws. The Supreme Court of Canada held in Whirlpool (supra 157-159) that the prohibition against double-patenting has two separate "branches": (1) the "same invention" branch, also known as the "coterminousness" branch; and (2) the "obviousness" branch. The "same invention" branch will invalidate any claim of a pending application or issued patent that is identical in scope to a claim of an earlier-issued patent. This branch is similar to "statutory" or "same invention" double-patenting in the U.S. The "obviousness" branch will invalidate any claim of a pending application or issued patent that is not patentably distinct (novel and non-obvious) from any claim of an earlier issued patent. This branch is similar to the judicially created doctrine of obviousness-type double-patenting in the U.S.

In the U.S., "statutory" ("same invention") double-patenting is fatal, whereas obviousness-type double-patenting can be obviated with a terminal disclaimer. A terminal disclaimer disclaims the non-overlapping term of the later-issued patent and also provides that the later-issued patent will cease to be enforceable if it does not remain commonly owned with the earlier-issued patent. In contrast, Canadian patent law does not provide any equivalent to a U.S. terminal disclaimer. Both "branches" of double-patenting are equally fatal in Canada and no direct procedural remedy exists to cure either branch. Due to this difference, greater care must be taken to avoid "obviousness" double-patenting situations in Canada that may have been dealt with by way of a terminal disclaimer in the U.S. counterpart.

Like the U.S., if a Canadian examiner effectively forces the filing of a divisional application by raising a lack of unity of invention objection (equivalent to U.S. restriction/election requirement), then the claims retained in the parent and the claims divided out are immune from double-patenting attacks based on one another. However, Canadian practice differs from U.S. practice on this point in that the limited immunity provided under Canadian practice is purely based on Canadian case-law (Consolboard Inc. v. Macmillan Bloedel Ltd., [1981] 1 SCR 504), whereas the similar immunity provided under U.S. practice is conferred directly from statute by 35 U.S.C. §121.

Typical double-patenting problems. In general, potential double-patenting risks may arise in any situation where the claims of one application arguably fail to recite any further non-obvious element or limitation in comparison to the claims of another co-pending application or issued patent.

One common scenario in which obviousness-type double patenting can arise relates to selection patents. For example, an initial patent application may be filed with claims to a broad class or genus of compounds. Subsequent work may identify a specific compound or species within the genus that has some advantage over other compounds within the genus, and a selection patent application may be filed with claims for the narrower species. The Supreme Court of Canada ruling in Sanofi-Synthelabo Canada Inc. v. Apotex Inc., 2008 SCC 61, has confirmed that selection patents are not, per se invalid for lack of novelty, obviousness or double-patenting. In this decision, the Court found that there was no double patenting in a later issuing selection patent claiming clopidogrel and its hydrogen sulfate salt over an earlier issued patent of the same applicant that claimed the genus encompassing clopidogrel and its salts. However, it is not uncommon for a narrower species application to proceed through examination to issuance more quickly than the earlier filed genus application. In the U.S., if the later-filed species application were to issue first, the still-pending genus application may receive an obviousness-type double-patenting rejection which, as noted earlier, could be overcome by filing a terminal disclaimer. In contrast, no procedural equivalent to a terminal disclaimer exists in Canada.

A further example stems from the fact that Canadian law does not include any direct equivalent of U.S. continuation practice. While Canadian practice does permit the filing of voluntary divisional applications (Canadian Patent Act, Subsection 36(2)), care must be taken to ensure that the claims that issue for a voluntary divisional application are patentably distinct (novel and non-obvious) from the claims of the parent. This can be particularly problematic if a voluntary divisional is filed to pursue the claims of a corresponding U.S. continuation that includes claims that are broader than those of the parent. Due to the absence of any terminal disclaimer or equivalent remedy in Canada, the issuance of the narrower parent claims while the broader divisional claims are still pending could prove fatal to those broader divisional claims.

Another common scenario arises when multiple applications with substantially identical disclosures but different claim sets are filed on the same day. Even if the independent claims of each application are directed to a different inventive concept than the independent claims of the other applications, the dependent claims often combine the various inventive concepts together, leading to double-patenting problems when one of the applications issues.

Strategies for avoiding double patenting problems. From a foreign practitioner's standpoint, a proactive measure to avoid double-patenting problems in Canada is to consolidate all related applications for the same applicant or assignee with a single Canadian patent agent and to inform the Canadian patent agent of the relationship. Even the most diligent Canadian practitioner will be unable to proactively avoid double-patenting problems if he or she is unaware that a related application is being prosecuted by another firm.

Developments in the prosecution of U.S. and other foreign counterpart and related applications may also serve as alarm bells to indicate that a review of related Canadian applications would be beneficial. In particular, whenever a terminal disclaimer is filed in the U.S., informing the Canadian agent and instructing him or her to conduct an immediate comparison of the two corresponding Canadian applications may be beneficial, to assess whether the absence of any equivalent terminal disclaimer procedure in Canada may pose obviousness-type double-patenting risks.

Claim consolidation is a valuable strategy for avoiding double-patenting problems in situations where multiple claim sets are supported by the specification of a single application. This may include situations involving a parent application and its pending or proposed divisional application, or situations involving multiple applications with substantially identical disclosures filed on the same day. Combining two desired claim sets into a single application will result in the examiner either allowing both claim sets to co-exist in the same application, or issuing a unity objection. The unity objection would then permit a divisional application to be filed, and the divisional and its parent would then enjoy a judicial immunity against double-patenting attack which they would not have enjoyed if the divisional had been voluntarily filed without any such objection. In either case, double-patenting risks are avoided.

For other situations, there are procedural mechanisms available under Canadian practice to control the relative timing of the applications. This control can be used to cause a broader "genus" application to issue before a narrower "species" application, thereby ensuring that the later-issued claims are inventive over the earlier-issued claims. The control of the timing of applications can also be used to keep a parent patent application pending as long as possible, until the applicant has determined all of the claims the applicant ultimately wants to pursue. The claims can then be consolidated into the parent application as discussed above, rather than filing a voluntary divisional application.

To control the relative timing of applications, a number of techniques are available to accelerate or decelerate the examination of an application. For example, one technique for decelerating examination is to defer the request for examination. Examination in Canada does not have to be requested until five years after the filing date.

Delaying the examination of an application may, however, be detrimental in the rare, though possible, situation where double patenting arises with a third party application or patent.

Conversely, techniques for accelerating examination are discussed in the concurrently published article titled, "Amendments to Canadian Patent Rules and Office practice bring opportunities for expedited patent examination", by Daphne C. Lainson.

Conclusions. Unwary applicants may face risks associated with one or more of the unique aspects of Canadian double-patenting laws. Fortunately, procedural mechanisms, such as those discussed above, are available to mitigate these risks.

The preceding is intended as a timely update on Canadian intellectual property and technology law. The content is informational only and does not constitute legal or professional advice. To obtain such advice, please communicate with our offices directly.

To print this article, all you need is to be registered on

Click to Login as an existing user or Register so you can print this article.

In association with
Related Video
Up-coming Events Search
Font Size:
Mondaq on Twitter
Register for Access and our Free Biweekly Alert for
This service is completely free. Access 250,000 archived articles from 100+ countries and get a personalised email twice a week covering developments (and yes, our lawyers like to think you’ve read our Disclaimer).
Email Address
Company Name
Confirm Password
Mondaq Topics -- Select your Interests
 Law Performance
 Law Practice
 Media & IT
 Real Estate
 Wealth Mgt
Asia Pacific
European Union
Latin America
Middle East
United States
Worldwide Updates
Check to state you have read and
agree to our Terms and Conditions

Terms & Conditions and Privacy Statement (the Website) is owned and managed by Mondaq Ltd and as a user you are granted a non-exclusive, revocable license to access the Website under its terms and conditions of use. Your use of the Website constitutes your agreement to the following terms and conditions of use. Mondaq Ltd may terminate your use of the Website if you are in breach of these terms and conditions or if Mondaq Ltd decides to terminate your license of use for whatever reason.

Use of

You may use the Website but are required to register as a user if you wish to read the full text of the content and articles available (the Content). You may not modify, publish, transmit, transfer or sell, reproduce, create derivative works from, distribute, perform, link, display, or in any way exploit any of the Content, in whole or in part, except as expressly permitted in these terms & conditions or with the prior written consent of Mondaq Ltd. You may not use electronic or other means to extract details or information about’s content, users or contributors in order to offer them any services or products which compete directly or indirectly with Mondaq Ltd’s services and products.


Mondaq Ltd and/or its respective suppliers make no representations about the suitability of the information contained in the documents and related graphics published on this server for any purpose. All such documents and related graphics are provided "as is" without warranty of any kind. Mondaq Ltd and/or its respective suppliers hereby disclaim all warranties and conditions with regard to this information, including all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement. In no event shall Mondaq Ltd and/or its respective suppliers be liable for any special, indirect or consequential damages or any damages whatsoever resulting from loss of use, data or profits, whether in an action of contract, negligence or other tortious action, arising out of or in connection with the use or performance of information available from this server.

The documents and related graphics published on this server could include technical inaccuracies or typographical errors. Changes are periodically added to the information herein. Mondaq Ltd and/or its respective suppliers may make improvements and/or changes in the product(s) and/or the program(s) described herein at any time.


Mondaq Ltd requires you to register and provide information that personally identifies you, including what sort of information you are interested in, for three primary purposes:

  • To allow you to personalize the Mondaq websites you are visiting.
  • To enable features such as password reminder, newsletter alerts, email a colleague, and linking from Mondaq (and its affiliate sites) to your website.
  • To produce demographic feedback for our information providers who provide information free for your use.

Mondaq (and its affiliate sites) do not sell or provide your details to third parties other than information providers. The reason we provide our information providers with this information is so that they can measure the response their articles are receiving and provide you with information about their products and services.

If you do not want us to provide your name and email address you may opt out by clicking here .

If you do not wish to receive any future announcements of products and services offered by Mondaq by clicking here .

Information Collection and Use

We require site users to register with Mondaq (and its affiliate sites) to view the free information on the site. We also collect information from our users at several different points on the websites: this is so that we can customise the sites according to individual usage, provide 'session-aware' functionality, and ensure that content is acquired and developed appropriately. This gives us an overall picture of our user profiles, which in turn shows to our Editorial Contributors the type of person they are reaching by posting articles on Mondaq (and its affiliate sites) – meaning more free content for registered users.

We are only able to provide the material on the Mondaq (and its affiliate sites) site free to site visitors because we can pass on information about the pages that users are viewing and the personal information users provide to us (e.g. email addresses) to reputable contributing firms such as law firms who author those pages. We do not sell or rent information to anyone else other than the authors of those pages, who may change from time to time. Should you wish us not to disclose your details to any of these parties, please tick the box above or tick the box marked "Opt out of Registration Information Disclosure" on the Your Profile page. We and our author organisations may only contact you via email or other means if you allow us to do so. Users can opt out of contact when they register on the site, or send an email to with “no disclosure” in the subject heading

Mondaq News Alerts

In order to receive Mondaq News Alerts, users have to complete a separate registration form. This is a personalised service where users choose regions and topics of interest and we send it only to those users who have requested it. Users can stop receiving these Alerts by going to the Mondaq News Alerts page and deselecting all interest areas. In the same way users can amend their personal preferences to add or remove subject areas.


A cookie is a small text file written to a user’s hard drive that contains an identifying user number. The cookies do not contain any personal information about users. We use the cookie so users do not have to log in every time they use the service and the cookie will automatically expire if you do not visit the Mondaq website (or its affiliate sites) for 12 months. We also use the cookie to personalise a user's experience of the site (for example to show information specific to a user's region). As the Mondaq sites are fully personalised and cookies are essential to its core technology the site will function unpredictably with browsers that do not support cookies - or where cookies are disabled (in these circumstances we advise you to attempt to locate the information you require elsewhere on the web). However if you are concerned about the presence of a Mondaq cookie on your machine you can also choose to expire the cookie immediately (remove it) by selecting the 'Log Off' menu option as the last thing you do when you use the site.

Some of our business partners may use cookies on our site (for example, advertisers). However, we have no access to or control over these cookies and we are not aware of any at present that do so.

Log Files

We use IP addresses to analyse trends, administer the site, track movement, and gather broad demographic information for aggregate use. IP addresses are not linked to personally identifiable information.


This web site contains links to other sites. Please be aware that Mondaq (or its affiliate sites) are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of these third party sites. This privacy statement applies solely to information collected by this Web site.

Surveys & Contests

From time-to-time our site requests information from users via surveys or contests. Participation in these surveys or contests is completely voluntary and the user therefore has a choice whether or not to disclose any information requested. Information requested may include contact information (such as name and delivery address), and demographic information (such as postcode, age level). Contact information will be used to notify the winners and award prizes. Survey information will be used for purposes of monitoring or improving the functionality of the site.


If a user elects to use our referral service for informing a friend about our site, we ask them for the friend’s name and email address. Mondaq stores this information and may contact the friend to invite them to register with Mondaq, but they will not be contacted more than once. The friend may contact Mondaq to request the removal of this information from our database.


This website takes every reasonable precaution to protect our users’ information. When users submit sensitive information via the website, your information is protected using firewalls and other security technology. If you have any questions about the security at our website, you can send an email to

Correcting/Updating Personal Information

If a user’s personally identifiable information changes (such as postcode), or if a user no longer desires our service, we will endeavour to provide a way to correct, update or remove that user’s personal data provided to us. This can usually be done at the “Your Profile” page or by sending an email to

Notification of Changes

If we decide to change our Terms & Conditions or Privacy Policy, we will post those changes on our site so our users are always aware of what information we collect, how we use it, and under what circumstances, if any, we disclose it. If at any point we decide to use personally identifiable information in a manner different from that stated at the time it was collected, we will notify users by way of an email. Users will have a choice as to whether or not we use their information in this different manner. We will use information in accordance with the privacy policy under which the information was collected.

How to contact Mondaq

You can contact us with comments or queries at

If for some reason you believe Mondaq Ltd. has not adhered to these principles, please notify us by e-mail at and we will use commercially reasonable efforts to determine and correct the problem promptly.