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Obviousness-type Double Patenting in Canada

January 17, 2013

Obviousness-type double patenting rejections that could easily be overcome in other countries can be impossible to overcome in Canada.  However, it is also relatively easy and inexpensive for patent applicants in Canada to avoid such rejections by including all of the desired claims in a single application, including those claims intended for divisional applications or U.S. continuing applications.

Protecting a single invention with two or more patents is prohibited in Canada.1 Obviousness-type double patenting prohibits claims from two different patents or pending applications from being obvious or not patentably distinct in view of one another.2 A patent examiner may reject claims of a pending application for double patenting as being obvious in view of claims of another pending application or issued patent. In Canada, these rejections cannot be overcome by making a terminal disclaimer, as is the case, for example, in the United States. Further, a court may find a divisional patent invalid for double patenting in view of the parent patent, despite the fact that both patents will expire on the same day.

Practical steps can and should be taken at the filing and prosecution stages in Canada to avoid obviousness-type double patenting rejections.

Multiple Canadian patent applications claiming different variants of what is arguably the same invention should be avoided, unless restriction is required by an Examiner. If multiple applications (including continuing applications) have been filed in another country, then these applications can be combined into a single application including:

1.  all of the claims of the multiple applications; and

2.  support in the description for all of these claims.

As there are no excess claim fees in Canada, this can considerably reduce filing expenses up front. If an Examiner raises a non-unity of invention objection and requires the application to be restricted to a single invention, then the non-elected claims may be included in divisional applications. Divisional applications filed in response to a non-unity of invention objection will be insulated from subsequent double patenting rejections based on each other and the parent application.3 Voluntary divisional applications, filed without such a non-unity of invention rejection, should be avoided.

A Canadian filing and prosecution strategy should involve consideration of obviousness-type double patenting rejections to enable patent applicants to avoid these rejections and reduce their upfront filing expenses by combining claims from multiple applications for variants of a single invention into one application.



1 Patent Act RSC 1954 c P-4, s. 36(1)

2 Whirlpool v. Camco (1999) 9 C.P.R. (4th) 129 (S.C.C.) when considering patents issued under the Patent Act as it read prior to 1989 when the term of a patent was 17 years calculated from the date of issue. Under the current Patent Act the term of a patent is 20 years calculated from the date of filing.

3 Consolboard Inc. v. MacMillan Bloedel (Saskatchewan) Ltd., (1981) 56 C.P.R. (2d) 145.


Maya Medeiros, B.Sc. (Comp. Sci. & Math), LL.B., is an associate lawyer in Bereskin & Parr LLP's Electrical & Computer Technology practice group.

Ian McMillan, B.Sc. (Math & Eng.), LL.B., LL.M., is a partner in Bereskin & Parr LLP's Electrical & Computer Technology practice group.


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Ian McMillan Ian McMillan
B.Sc. (Math & Eng.), LL.B., LL.M.
905.817.6103  email Ian McMillan