Double patenting refers to the granting of two patents for a single invention in the same country to the same patentee. This article will explore the approach taken by Canada, the United States and Europe on this issue.


There are no statutory provisions specifi cally addressing the issue of double patenting in Canada although Canada’s Patent Act states, “A patent shall be granted for one invention only.”1 In Whirlpool Corp. v. Camco Inc.,2 the Supreme Court of Canada (SCC) interpreted this section to mean that an inventor is only entitled to a single patent for each invention and therefore double patenting is prohibited. The SCC defi ned two distinct branches of double patenting. The “same invention” branch occurs in situations where the claims of one patent are identical to claims of another patent granted to the same patentee. The second branch, “obviousness” double patenting, prohibits the issuance of a second patent with claims that are not “patentably distinct” from those of an earlier patent. More recently, in GlaxoSmith- Kline Inc. v. Apotex Inc.,3 the Federal Court found that a divisional application may be rejected if its claims lack novelty or ingenuity over the claims of the parent patent.  

The Canadian Intellectual Property Offi ce (CIPO) cites these two cases as the basis for requiring that claims in a divisional application be novel and non-obvious over claims in a parent application. A number of Canadian examiners even extend this interpretation to co-pending applications by the same applicant where one is not a divisional of the other.

The Patent Act does not contain any provisions addressing the patentability of related unpublished applications from the same applicant, but it does require an invention be novel over unpublished co-pending applications from a different applicant.4 However, there is no statutory requirement that an invention be non-obvious over unpublished copending applications from a different party. Thus, applicants in Canada can face the unreasonable situation where CIPO raises an “obviousness” rejection based on a commonly owned, co-pending application, but not where the applications are owned by different parties.  

In Consolboard Inc. v. MacMillan Bloedel,5 the SCC indicated, “If patents are granted on divisional applications directed by the Patent Offi ce, none of them should be deemed invalid, or open to attack, by reason only of the grant of the original patent.” It appears therefore, that once an examiner has required a division during prosecution, no subsequent attack for obviousness double patenting can be raised.  

In Canada, the fi ling of voluntary divisional applications is not recommended. Instead, it is suggested that claims intended for division be added to the parent application while it is still pending. This might provoke a non-unity objection from the examiner after which a divisional application may safely be fi led and any subsequent double patenting objections may be addressed on the basis that the divisional application was required by the examiner. Alternatively, the claims will issue in a single patent and such a patent may not be deemed invalid by reason only that it has been granted for more than one invention.6  

United States

The U.S. patent law allows the fi ling of divisional, continuation and continuation- in-part applications, which often results in the issuance of multiple closely related patents. Similar to Canada, the United States Patent and Trademark Offi ce recognizes two types of double patenting: “anticipation” or “statutory double patenting” and “obviousness” or “non-statutory double patenting.” Statutory double patenting fi nds its basis in the United States Code7 and is raised when the claims or two commonly owned patents are identical in scope. Non-statutory double patenting is a judicially created doctrine grounded in public policy, with the primary intent to prevent prolongation of the patent term by prohibiting claims in a second patent to the same applicant that are not patentably distinct from claims in a fi rst patent. Despite the long-established prohibition against double patenting,8 and in contrast with Canada, under U.S. practice, a non-statutory double patenting objection may be overcome by the fi ling of a “terminal disclaimer”9 such that the patents in question will expire on the same date and will always be commonly owned.10


The European Patent Convention (EPC) does not deal explicitly with double patenting. However, the European Patent Offi ce11 and the Enlarged Board of Appeal12 take the view that it is an accepted principle in most patent systems that two patents cannot be granted to the same applicant for one invention, and that an applicant has no legitimate interest obtaining two patents with substantially identical claim scope.  

In 2000, the Boards of Appeal (BoA) found there was no provision in the EPC that would prohibit a divisional application from containing broader claims than those of the parent application.13 Despite some suggestions to the contrary,14 the most recent decisions of the BoA follow this conclusion and allow an applicant to obtain a second patent for related subject matter, provided there is at least one technical feature distinguishing the claims of two patents.15 Indeed, in a recent decision, the BoA found an applicant could have a legitimate interest in obtaining two patents with substantially identical claim scope where the later patent claimed priority to the earlier patent.16  

Therefore, although the situation is somewhat confused in Europe, it appears there is no prohibition under the EPC to the granting of two commonly owned patents having similar claim scope provided they are at least notionally different in their scope of protection.  

If you are involved in patenting across multiple jurisdictions, well-informed patent counsel can help guide you through the process, ensuring you comply with the requirements of the various patenting authorities.