Canada’s Intellectual Property Firm

Three key differences between U.S. and Canadian patent law that can affect patent filing strategies in Canada

Authored byChristine Genge

Our patents team have published a comparative guide to double patenting in Canada and US. This guide looks at similarities and differences between the Canadian and U.S. double patenting doctrines are discussed in this article and some strategies are identified for mitigating double patenting risks in Canada.

Though there are many similarities between U.S. and Canadian patent law, the following significant differences can affect the key decision of whether to file in Canada.

1. Grace period time limit

Sections 28.2 and 28.3 of Canada's Patent Act provide a grace period for pre-filing disclosures originating from the applicant that would otherwise be citable for anticipation and obviousness. These sections contain common language that should be kept in mind when developing filing strategies. In particular, both sections refer to a disclosure that occurred "more than one year before the filing date." This "filing date" is that of the Canadian application, not the Convention priority date. (In the case of a PCT national phase application, the Canadian filing date is deemed to be the PCT international filing date.).

A typical hypothetical scenario frequently encountered by a Canadian patent practitioner is that an invention was disclosed by the inventor (or someone deriving knowledge from the inventor) on October 1, 2007, and a U.S. provisional (or regular) application claiming that invention was filed on September 1, 2008, within one year of the disclosure. The question often posed is, can an application be filed in Canada on September 1, 2009, which claims priority from the U.S. application? Unfortunately, the answer is no. The fact that the priority application was filed within one year of the disclosure is irrelevant. The Canadian filing date must be no more than one year after the disclosure.

Practically speaking, this means that where there is a pre-filing disclosure, it may be prudent to file concurrently in the U.S. and Canada, since a priority claim does not extend the grace period for filing in Canada.

2. No on-sale bar

What constitutes a disclosure is also defined by sections 28.2 and 28.3 of the Patent Act. In Canada, a disclosure occurs when the subject matter defined by a claim in an application for a patent is disclosed "in such a manner that the subject matter became available to the public in Canada or elsewhere." A leading case on what "available to the public" means where there has been a sale is Baker Petrolite Corp. v. Canwell Enviro-Industries Ltd.2002 FCA 158. In Baker Petrolite, the Federal Court of Appeal laid out a number of principles governing when an invention has been made available to the public. Among the principles laid out is that a sale to the public alone is not always a disclosure within the meaning of sections 28.2 and 28.3. Thus, there is no absolute "on-sale bar" in Canada. It is possible for an invention to be sold but, due to the nature of the invention, if the product sold cannot be reverse-engineered to reveal the subject matter of the invention, then there is no disclosure.

U.S. practitioners familiar with this methodology should therefore keep in mind that even though the U.S. on-sale bar may operate to prohibit a U.S. patent from being obtained, it may still be possible to obtain a patent in Canada.

3. No terminal disclaimer

Terminal disclaimers are relevant in the context of double patenting. The Supreme Court of Canada, in Whirlpool Corp. v. Camco Inc.2000 SCC 67, confirmed that there are two types of double patenting. One is same-invention double patenting, where the two claims are coterminous, and the other is obviousness-type double patenting, where a claim is obvious in view of the other set of claims. Such an objection can be raised against parent and divisional applications. The objection can be raised regardless of whether the applications have a common priority claim.

Where a double-patenting objection is raised in Canada, the question sometimes posed by practitioners familiar with U.S. law is whether a terminal disclaimer can be entered to overcome the double-patenting objection. Unfortunately, Canadian law does not include a terminal disclaimer practice. If a double-patenting objection can not be overcome by argument, the claims will need to be amended to eliminate the overlap.

In practice, where an applicant has new claims that might be filed in a divisional or continuation application in the U.S., it may be prudent in Canada to add those claims to the parent application and wait to see if there is an objection that requires that the claims be divided out, rather that voluntarily filing a divisional application that may be subject to a double-patenting objection.


Canadian filing strategies to consider include:

  • if there has been a pre-filing disclosure of the invention by the inventor, file a patent application in Canada concurrently with filing in the U.S., or no later than one year from the date of disclosure;
  • if there has been a sale outside the grace period, consider whether it is enabling; if not, it may still be possible to file a patent application in Canada despite the on-sale bar in the U.S.; and,
  • where new claims are being filed in a U.S. continuation or divisional application, add the new claims to the parent application in Canada, rather than voluntarily filing a divisional application because there is no terminal disclaimer to cure a double-patenting objection in Canada.

If you have any questions about these changes and how they may affect you or your organization, please contact a member of our Patents practice group.

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