18 November 2021

Doubling Down – Prohibition of Double Patenting Affirmed at the EPO

Through the issuing of decision G 4/19, the Enlarged Board of Appeal (Enlarged Board) has established the legal basis for the prohibition of double patenting. But what does this mean for applicants at the European Patent Office (EPO)? Does it indicate a change in practice, or does it just make official the stance that examiners are already taking during examination? And what further developments should we expect and prepare for?

The restriction on double patenting, that is the ability for the EPO to refuse a European application if it claims the same subject-matter as a European patent granted to the same applicant and with the same effective date, has long been a contentious issue at the EPO. The concept of double patenting is not explicitly mentioned in the European Patent Convention (EPC), yet many at the EPO have felt that there is no legitimate reason for an applicant to have two patents granted for the same invention. Therefore, the EPO has relied on interpretation of more general provisions of the EPC in order to raise a double patenting objection, with applicants arguing in response that there is no legal basis for doing so. Slowly, a body of case law from the Boards of Appeal has built up in support of the prohibition and examiners have been able to raise objections with more confidence, but there has been some inconsistency in how cases have been decided. G 4/19 has now brought some clarity to this area.

The referral

In 2019 the Board of Appeal, in decision T 318/14, referred three questions to the Enlarged Board to seek a definitive answer as to whether a European application could be refused for double patenting and under what circumstances. The Enlarged Board accepted the referral as G 4/19. The subject application in T 318/14 claims priority from an earlier European application. The priority application was granted by the EPO and the pending claims for the subject application were completely identical to those granted for the priority application. The examining division therefore refused the application on the grounds of double patenting and the applicant filed the appeal to challenge that decision. However, the Board of Appeal could find no clear legal provision supporting the prohibition of double patenting, so it asked the Enlarged Board whether an application can be refused for double patenting and if so, what the conditions are for such a refusal.

The prohibition has basis in law

The Enlarged Board answered the first referred question in the affirmative, confirming that the prohibition of double patenting does find basis in law. In particular, it stated that a European patent application can be refused under Articles 97(2) and 125 EPC if it claims the same subject-matter as a European patent which has been granted to the same applicant and does not form part of the state of the art pursuant to Article 54(2) and (3) EPC.
With the second referred question, the Board of Appeal wanted to clarify the relationship that is required between the granted patent and pending application for the prohibition to apply. This was of particular relevance because the patent and application of the referral did not have the same filing date and so it was argued that there was a legitimate interest in such circumstances in obtaining grant of the pending application despite the duplication of the subject-matter from the granted priority application (i.e. due to the benefit of up to an additional year of protection). However, the Enlarged Board decided that an application can be refused irrespective of whether it:

(a) was filed on the same date as;

(b) is an earlier application or a divisional application in respect of;


(c) claims the same priority as, the European patent already granted.

The third referred question was directed at whether there is a legitimate interest in the grant of both the priority application and the subsequent application for the same subject-matter, due to the difference in the filing date and so term of the patent. However, the Enlarged Board decided an answer to that question was not required following its answer to the second question.

A missed opportunity?

The Enlarged Board deliberately did not consider any questions regarding the meaning of “the same subject-matter” or “the same applicant” in the prohibition, despite being asked to do so, because it defined such considerations as outside the limits of the referral. This is a shame, because there is clearly uncertainty on these points and there is likely to be a need for additional referrals in the future to address them.

The question of what constitutes same subject-matter may cause particular difficulty for applicants. In the referral decision of course, the claims of the pending application were completely identical to those of the granted patent, so they clearly covered the same invention and subject-matter. On the other hand, for a patent and application that claim distinct inventions, invention A and invention B respectively, it is clear that they do not claim the same invention even if the later application also claims B+A, perhaps through a dependent claim; it is confirmed in the Guidelines for EPO examiners (GL; here) that this is generally permissible.

The situation in reality though, is often not so clear-cut. It is accepted that an applicant may legitimately want to obtain quick protection for a preferred embodiment and then pursue the general teaching in a divisional application (see G 2/10 and GL), and that merely a partial overlap in scopes of protection is fine (see T 877/06 referenced in GL). But how “partial” does a “mere partial overlap” have to be? Is it permissible for a dependent claim or particular combination of dependent claims in a broader divisional application to have complete identity with the narrower granted parent? There is some ambiguity on these points, which can cause difficulties for applicants.

Impact of the decision

The most obvious implication of the decision G 4/19 is that applicants who file a European priority application will need to carefully consider the fate of that application. If the priority application is allowed to grant, then it will be difficult to pursue a subsequent, priority claiming application to the same subject-matter, despite the extra term of protection that the subsequent application might provide.

A more subtle impact though is likely to be an emboldening of examiners when it comes to making double patenting objections. Indeed, whereas in the past, double patenting might only be mentioned if and when there was clear conflict between the claims of a pending application and its related application or patent, some examiners have already begun to routinely warn about the prohibition of double patenting in communications for divisional applications. The frequency of such general warnings and the frequency with which double patenting objections are actually raised, is likely to increase now that the examiners can point to decision G 4/19 as providing a clear legal basis for a double patenting objection.

We will get an indication of the likely impact of the decision on examiner behaviour when we see any updates on the subject of double patenting that are made to the GL – the next version should publish in February 2022 and then enter into force the following month.

Expectations for the future

It is difficult to predict with any certainty how the law and practice around double patenting will develop at the EPO. As mentioned above, it seems likely that examiners will be emboldened by decision G 4/19 and we are already seeing more mention of double patenting by examiners during the prosecution of divisional applications.

One concern is that examiners may seek to pursue objections more aggressively when there is not complete identity of claimed subject-matter, but instead where there is partial overlap. In particular, we may start seeing examiners objecting to broader applications that wholly encompass narrower embodiments already granted, for example in the “narrow parent/broader divisional” type situations described above. Indeed, we are already seeing indications that some examiners are moving in this direction, with warnings issued during prosecution to avoid overlap with a parent patent where any claim of a divisional claims the same invention as any claim of the parent.

Examiners might, perhaps, seek to further challenge the presence of overlap along the lines of obiter dictum in decision G 2/10. As stated above, decision G 2/10 affirms the legitimacy in pursuing a narrow parent patent and then a broader divisional application. However, G 2/10 was about disclaimers and that decision also suggests, with reference to the “narrow parent/broader divisional” situation, that in such circumstances, a disclaimer could be used to avoid a prohibition on double protection i.e. to remove any overlap at all between the scope of the two claim sets. The idea of the possible need for such a disclaimer at the EPO, perhaps to remove the specific embodiment of the granted parent from the claims of the divisional so as to eliminate any overlap at all, is worrying, not least because such preferred specific embodiments are often the most well described, supported, and exemplified in the application as filed. Thankfully, any argument about the need for such a disclaimer should be easy to rebut at the moment, not least because the Enlarged Board in decision G 4/19 did state that “Secondly, the distinction between double protection (claims with overlapping scope) and double patenting also needs to be kept in mind” (see paragraph 2 of the reasons for the decision).

If we are correct in some of our predictions regarding examiner behaviour, then there is likely to also be resistance from applicants, which would naturally lead to another Enlarged Board referral on the subject of double patenting in due course, perhaps focused on the “same subject-matter” requirement of the prohibition. In the meantime, applicants should be mindful of the potential for double patenting objections when they have multiple applications with the same effective date and might consider carefully planning claim strategies to minimise the likelihood and impact of such objections.