Double patenting in Canada: 5 pitfalls and how to avoid them

Double patenting (in other words, obtaining more than one patent for an invention) is prohibited in Canada and is a ground for invalidity.

The concept of double patenting can pose a significant challenge for applicants and practitioners, particularly when managing large international portfolios and attempting to align international prosecution strategies with commercial goals.

In this article we summarize 5 of the most common pitfalls relating to double patenting that are encountered in Canada, and we offer steps for how to avoid them.

Pitfall 1: Voluntary Divisionals – avoid them!

Probably the most common situation that applicants will face which requires assessing the risk of double patenting is the question of divisionals.

A divisional application that is filed voluntarily runs the risk of invalidity if it is determined by a court that the claims of the divisional are not patentably distinct from the parent.

Historically, the courts have determined that double patenting does not apply to a divisional that was filed at the direction of the Patent Office, i.e. due to a unity objection.^[1]

While recent jurisprudence has clarified that this immunity is not automatic,^[2] it is still advisable to purposefully try to elicit unity objections early on in prosecution so that any subsequent divisionals based on the unity objection are insulated from double patenting allegations. For example, a variety of independent claims that are directed at potentially different inventions may be included in the claim set to be examined. In Canada, there are fortunately no restrictions on when claims can be added to an application and there is no limit on the number of independent claims that may be presented. However, it is worth noting that excess claim fees are payable for claims above 20.

• Voluntary divisionals should be avoided and divisionals should only be filed where there is explicit direction from the Patent Office.

Pitfall 2: Related applications - be portfolio aware

It is also not uncommon for applicants to prosecute several related patent applications simultaneously with the intention of covering different aspects of the same technology. Regardless of whether these co-pending applications have the same filing date or different filing dates, a potential double patenting risk exists if a court finds that the claims are not patentably distinct. Unlike jurisdictions such as the US,^[3] there is no “terminal disclaimer” practice in Canada to insulate co-pending applications from a double patenting attack. Therefore, any overlapping subject matter identified in the claims of two co-pending applications should be removed. Alternatively, one of the two applications could be withdrawn or allowed to go abandoned.

Similarly, some applicants choose to split the subject matter of an invention into one or more patent applications for the purpose of licensing each aspect separately. While this strategy may be legitimate in other jurisdictions, it is not advisable in Canada due to double patenting risks. Instead, the subject matter should be prosected in a single application, except in the case that a unity objection is raised.

• All applications in an applicant’s portfolio should be identified and assessed for double patenting risks in order to inform the prosecution strategy.

Pitfall 3: Order of grant – timing matters

Double patenting specifically prohibits the grant of a subsequent patent to the same invention.^[4] In practice, this means that where two patents are granted to the same subject matter, it is the later granted patent that is invalid for double patenting. Therefore, when prosecuting related applications it is preferable to allow the most commercially valuable patent to proceed to grant first.

Various mechanisms exist for speeding up or slowing down prosecution to achieve grant in the order of preference, including filing a request for accelerated examination and making use of the reinstatement procedure.

• If in doubt, ensure that the most valuable patent proceeds to grant first.

Pitfall 4: Don’t forget obviousness

The Canadian courts have held that two types of double patenting are prohibited: (i) same invention type; and (ii) obviousness-type. Same invention type double patenting occurs when the claims of two patents are “identical or conterminous” and obviousness-type double patenting occurs when the later set of claims is not “patently distinct” from the claims of the earlier patent. This distinguishes Canadian practice from other jurisdictions such as Europe, China and Japan where only same invention type double patenting exists.

The assessment for obviousness-type double patenting is similar to the assessment of obviousness with respect to prior art documents, except that only the claims of the earlier patent application are relevant to the assessment.

Selection patents are at risk of an obviousness-type double-patenting challenge, as a species claim likely would not be identical to a corresponding genus claim but potentially may not be patentably distinct from the genus claim. However, if the species selection is determined to relate to a “special advantage” which is possessed by the species relative to the genus, then the species patent should be held to be patentably distinct and would not be invalid for obviousness type double patenting.^[5]

• Even if claims of two applications are not identical, the claims should be assessed for obviousness type double patenting.

Pitfall 5: Check your dependent claims – all claims count

As noted above, when assessing double patenting the Canadian courts will review the claims of the two applications in question to determine whether there is (i) same invention type or (ii) obviousness-type double patenting.

While the independent claims are of primary interest, the dependent claims are also relevant. For example, features in the dependent claims of the earlier patent may be used to allege double patenting against a later patent, if the subject matter claimed in the later patent is deemed identical to, or an obvious alternative to, the dependent claim features of the earlier patent.^[6]

• All claims including the dependent claims should be reviewed when assessing double patenting risks