Double patenting, i.e. where an applicant attempts to cover "the same subject-matter" with two patents and neither patent is citable prior art for the other, can occur when the same applicant files: (1) two applications on the same day, (2) parent and divisional applications, or (3) a priority-founding application and a subsequent priority claiming application. If both applications claim the same subject-matter at the grant stage, one may be prevented from proceeding to grant unless it is amended to define a different scope of protection than the other.

The prohibition on double patenting in Europe is based on the idea that an applicant has no legitimate interest in the second patent for the same subject matter if they already possess one granted patent for that subject matter (G1/05 and G1/06). The European Patent Convention itself however does not explicitly mention double patenting.

One of the new referrals to the Enlarged Board of Appeal (EBA) (from T0318/14), which at the time of writing does not have a referral number, seeks to determine the criteria for refusal of an application in the three situations mentioned above. The full referral questions are as follows:

1. Can a European patent application be refused under Article 97(2) EPC if it claims the same subject-matter as a European patent granted to the same applicant which does not form part of the state of the art pursuant to Article 54(2) and (3) EPC?

2.1 If the answer to the first question is yes, what are the conditions for such a refusal and are different conditions to be applied where the European patent application under examination was filed

a) on the same date as, or

b) as a European divisional application (Article 76(1) EPC) in respect of, or

c) claiming the priority (Article 88 EPC) in respect of a European patent application on the basis of which a European patent was granted to the same applicant?

2.2 In particular, in the latter case, does an applicant have a legitimate interest in the grant of the (subsequent) European patent application in view of the fact that the filing date and not the priority date is the relevant date for calculating the term of the European patent under Article 63(1) EPC?

Scenarios 2.1a and 2.1b relate to situations when both cases have the same effective filing date and therefore, crucially, the same expiry date. The scenario set out in 2.1c relates to the situation where one of the two cases is a priority founding application and the other of the two is the priority claiming application, thus leading to the situation where the two applications do not have the same effective filing date. This means that the later filed application, if granted, could in effect be used to extend protection by up to a year.

Historically, double patenting may also be assessed by the Intellectual Property Office of individual EPC states under their national law. For example, under UK law, if it appears that a UK patent and a corresponding European patent have both been granted for the same invention, having the same priority date, and that the application for the patents were filed by the same applicant or their successor in title, the Comptroller General of Patents has the power to revoke the UK patent granted under the UK Patents Act (Section 73(2)).

Were the EBA to decide that double patenting is solely a matter for national law, EPO Examiners should, contrary to the current practice, stop raising objections on this ground. The matter would then be considered upon grant and validation by the national Intellectual Property Offices.

To clarify the existing practice of the EPO determining whether the applicant has a "legitimate interest" in both patents, in section 2.2 of the referral, the question is raised as to whether an applicant can have a legitimate interest in the grant of two patents claiming the same subject matter, but having different effective filing dates and therefore expiring on different dates. Obviously, there is a "business interest" in extending the protection provided by a granted patent by up to an extra year, or else this referral wouldn't exist, but the question is whether that constitutes a "legitimate interest".

I for one am interested to see if the EBA makes reference to Article 87 of the EPC or to Article 4 of the Paris Convention when considering question 2.1c. The respective Articles use slightly different wording to define the priority right and do not, necessarily, lead towards the same answer to this question. This case potentially raises the question of whether the priority period as set out in the Paris Convention was ever intended to be used to extend the possible period of protection beyond 20 years, and whether this is indeed a legitimate use of the priority period.

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