Double patenting and divisionals in Canada: evolving strategies for applicants

Double patenting and unity of invention in divisional practice remain central issues in patent prosecution in different jurisdictions, but the strategies for addressing them differ sharply between Canada, the United States and Europe. The basic doctrine against double patenting prevents the same applicant from obtaining more than one patent that claims the same subject-matter or, in many jurisdictions, claims that are not patentably distinct, with the precise tests and any cures determined by local law. In the United States, terminal disclaimers are available to cure non-statutory obviousness-type double patenting. In Europe, unity requirements are strictly enforced, and the EPO may refuse an application on the grounds of double patenting, but this is limited to “same subject-matter” refusals. In Canada, however, the critical factor is whether a divisional application was filed “on the direction of the Commissioner”. Subsection 36(2.1) of the Patent Act makes this a focal point, which in practice affects divisional immunity and makes it prudent for applicants in Canada to consider how unity objections are raised and how the prosecution record is built.¹

The Canadian framework

A "divisional application" is a later application carved out of a parent application that shares the parent's filing date under subsection 36(4) and retains any applicable priority date for the divided subject-matter and is prosecuted separately. A divisional application may be filed either voluntarily under subsection 36(2), or on the direction of the Commissioner under subsection 36(2.1), provided filing occurs before grant of the parent.

Subsections 36(2) and 36(2.1) of the Patent Act provide as follows:

• (2) “Where an application (the “original application”) describes more than one invention, the applicant may limit the claims to one invention only, and any other invention disclosed may be made the subject of a divisional application […]”
• (2.1) “Where an application (the “original application”) describes and claims more than one invention, the applicant shall, on the direction of the Commissioner, limit the claims to one invention only, and any other invention disclosed may be made the subject of a divisional application […]”

(emphasis added)Subsection 36(2.1) provides the statutory basis for what is often referred to as “divisional immunity”. Canadian courts have recognized a safe harbour where division is on the direction of the Commissioner, rooted in Consolboard v MacMillan Bloedel and developed in subsequent jurisprudence.² If a divisional is filed in response to such a direction, it benefits from the safe harbour against later double patenting attacks. Voluntary divisionals, filed without any explicit direction, remain vulnerable. Courts have repeatedly confirmed this distinction, from Whirlpool v Camco at the Supreme Court³ to Bayer v Cobalt at the Federal Court of Appeal,⁴ and more recently in NCS Multistage v Kobold, where the Federal Court emphasized that the origin of a divisional application must be traceable back to the Commissioner’s direction.⁵

Nevertheless, the jurisprudence regarding the circumstances under which a divisional is considered filed on a direction of the Commissioner, and thus potentially immune from double patenting, versus when it is filed voluntarily, is in flux. In Abbott Laboratories v Minister of Health and Sandoz, the Federal Court found that a divisional application filed in response to a unity of invention objection was not invalid for double patenting, as it would be “unfair and inequitable” to invalidate a patent for following the Commissioner’s directions.⁶ On the other hand, the Court in Biogen v Taro Pharmaceuticals indicated that a divisional application filed after a non-final unity objection was voluntary, as the objection was not a rejection by way of a “final action”.⁷ Notably, neither Abbott nor Biogen appears to consider the distinction between subsections 36(2) and 36(2.1). Most recently, in NCS Multistage, Justice McVeigh parsed the language of these provisions and divergence in the case law regarding what might constitute a voluntary or forced divisional patent. When an applicant files a voluntary divisional, the divisional and the parent application must each disclose a different invention at their core (i.e. patentably distinct) to avoid a double patenting challenge. Further, Justice McVeigh stated that “[t]he preferred approach is an informed middle ground” and articulated a traceability approach, i.e., double patenting immunity applies where the origin of the divisional can be traced back to a direction of the Commissioner.⁸

This concept of “traceability” is becoming central in Canadian jurisprudence. What remains unsettled is the level of formality required: whether the examiner’s requisition must explicitly reference subsection 36(2.1), or whether an indication that the applicant must elect one invention suffices. Regardless of whether subsection 36(2.1) is explicitly invoked, a further safeguard may be to ensure the divisional claims are patentably distinct from the parent, as Canadian law provides no terminal disclaimer and immunity doctrine continues to evolve.

Strategic considerations in Canada

One avenue to strengthen divisional immunity is to consolidate claim sets during prosecution. Consolidating can help minimize the double patenting risk of overlapping claim scope across multiple applications, streamline examination, and reduce the likelihood of voluntary divisionals being pursued without unity protection. Applicants should avoid trimming claim groups in a parent application before the examiner issues a unity objection. Allowing the examiner to issue a formal unity objection not only creates the statutory basis for division but also ensures that the resulting divisional has stronger protection.

Canadian practice now also requires careful consideration of excess claim fees and limited office actions. For examinations requested on or after October 3, 2022, fees apply to each claim beyond twenty, and these must be paid at the time of requesting examination and reassessed again at allowance, calculated on the greatest number of claims pending at any time after the examination request.⁹ In parallel, examination is constrained by a limited number of office actions, with further prosecution requiring a Request for Continued Examination (RCE) after three examiner notices on the merits, and after every two further notices following an RCE.¹⁰ These cost and procedural changes make it even more important to plan claim groupings strategically, balancing the risk of losing safe harbour by trimming claims before a unity objection against the cost impact of carrying large claim sets into examination. It is advisable for applicants to consider the claims across all jurisdictions to put all subject matter of interest before the examiner in the first instance. See our recent article for a more detailed discussion of unity of invention prosecution strategies.

Given the evolving case law, it may be prudent for applicants to seek explicit confirmation that a unity objection is made "on the direction of the Commissioner". A request that the examiner indicate on the record that "according to subsection 36(2.1) of the Patent Act, the applicant shall, on the direction of the Commissioner, limit the claims to one invention only, and any other invention disclosed may be made the subject of a divisional application" would help clarify the record. The law has not yet confirmed whether explicit statutory reference is required or whether a general unity objection suffices. Currently, when issuing a unity objection, examiners typically reference subsection 36(2), stating that after limiting the claims to one invention only, the applicant may make any other invention disclosed the subject of a divisional application. Given the lack of reference to a direction of the Commissioner under subsection 36(2.1), applicants may wish to reference subsection 36(2.1) in electing a group in response to a unity objection. The safer course of action is to place as much supporting material on the record as possible, so that the file history demonstrates traceability back to the Commissioner’s direction.

Comparative perspective

In the United States, both same-invention and obviousness-type double patenting are recognized. Although same-invention double patenting is fatal, terminal disclaimers are a ready and effective solution to overcome obviousness-type double patenting.¹¹ Restriction requirements compel applicants to elect claims, but even voluntary continuations and divisionals can be salvaged through disclaimers. See our article for an in-depth comparison of double patenting in Canadian and US practice.

In Europe, unity of invention is applied stringently at the search and examination stages. Applicants are required to elect one invention and may, within the strict pendency window, file divisionals for unelected inventions.¹² There is no European equivalent to Canada’s “Commissioner’s direction”, and it is the EPO’s position that an application can be refused under Articles 97(2) and 125 of the European Patent Convention (EPC) where it claims the same subject matter as an earlier European patent to the same applicant, as confirmed in decision G 4/19.¹³ However, the European “same subject-matter” approach to double patenting provides some breathing room for applicants by removing the risk of obviousness-type double patenting. This allows European applicants to obtain coverage for partially overlapping subject matter, so long as the claims are not identical in scope. For example, applicants may first pursue a narrow set of claims to quickly obtain protection and then subsequently seek protection of the broader genus. While such strategies are possible in both Europe and the United States, this may result in a fatal obviousness-type double patenting objection in Canada.

In Canada, the absence of terminal disclaimers and the reliance on subsection 36(2.1) creates a narrower, more cautious path. Immunity may be available, but only if the divisional application can be demonstrably traced to the Commissioner’s direction. By contrast, voluntary divisionals do not benefit from this statutory protection and may still face double patenting objections, which must then be addressed on the basis of claim distinctness. The prudent course is to further ensure the divisional claims are patentably distinct from the parent to minimize risk.

Conclusion

For applicants prosecuting families across jurisdictions, the Canadian position requires particular care. Excess claim fees and the RCE framework make proactive claim planning relevant for controlling prosecution costs. Consolidating claim sets reduces overlap between related applications to mitigate the risk of double patenting. Managing the record to secure a formal unity objection may preserve divisional immunity and inviting examiners to reference subsection 36(2.1) reduces ambiguity. Canadian case law on double patenting and divisional immunity is still evolving, and traceability is the touchstone