Originally posted on IPKat.
For those wondering about the risks of inconsistencies and description amendments following the G1/24 and G1/25 duo, the Board of Appeal also found that an “unresolved ambiguity” in the claims added subject-matter by virtue of the fact that both possible interpretations were considered covered by the claim.
Legal background: Ambiguity and added matter, a divided case law
Article 123(2) EPC prohibits amendments that extend beyond the content of the application as filed. The test is the “gold standard” of G 2/10: what the skilled person would derive directly and unambiguously from the application as filed.
The intention of the referring Board in G 1/26 is to resolve confusion in the case law over how ambiguous claim interpretations interact with the added matter test. T 1791/16 held that all technically reasonable interpretations of an ambiguous claim must be considered, and that if any one of them extends beyond the application as filed, there is added matter. A different line of case law, including T 367/20, says that the claim should first be interpreted by the skilled person, and only then compared against the application as filed. We also, of course, now have the decision of the EBA in G 1/24 that the description must always be “consulted” when interpreting the claims (Evolve Insights).
This divergence led to the referral in T 873/24, now pending as G 1/26 (Evolve Insights). Question 3(a) of G1/26 asks whether a claim term must be assessed for added matter against all interpretations that make technical sense on the basis of the claim alone. Question 3(b) asks, if this is not the case, whether if it sufficient that only the interpretations of the subject-matter of the claim established against the background of the patent specification as a whole are directly and unambiguously derivable from the application as filed.
Notably, the recent decision in G 1/25 went a fair way towards answering the G 1/26 questions on claim interpretation, confirming that interpretation is a single process and that the description cannot impose a limitation for which the claim wording provides no basis. The added matter question, however, was left without a direct answer (Evolve Insights).
Case background: Back to cigarettes
In this case we are unfortunately back to the rather uninspiring subject matter of cigarette inventions (who knew there was so much important innovation in the field…). Philip Morris’s patent, EP 3288403 B1, related to a cartridge (or “cartomiser”) for an e-cigarette. The cartridge was specified as combining a housing holding the liquid substrate with a heater assembly, the heater element of which extends across the opening of the housing and has apertures of different sizes. Nicoventures Trading Limited opposed. The Opposition Division maintained the patent in amended form, and the Patentee appealed. The key prior art was an earlier-filed but later-published international application, relevant to novelty only under Article 54(3) EPC.
Providing or fixing
Claim 12 as granted was a method of manufacturing the cartridge, requiring only “providing” a storage portion, filling it, and “providing” a heater assembly extending across the opening. The Patentee argued that the skilled person would read the claim as requiring the heater assembly to be fixed to the housing, as the only technically reasonable reading.
The Board of Appeal was not convinced, finding that “The notion of “providing” per se covers the mere act of “making available”” (r. 5). However, having consulted the description, the Board of Appeal concluded that “Claim 12 has thus deliberately been formulated without indicating how the “provided” components are further handled in the claimed manufacturing method” (r. 7.3).
The decision was taken at oral proceedings on 30 July 2026, before G 1/25 issued on 3 September 2026. The written reasons nonetheless added that the Board of Appeal had not “used the description or drawings to impose on claim 12 a limitation for which the claim wording provides no basis” (r. 7.5), in line with G 1/25. Critically, only one paragraph expressly stated that the heater assembly was fixed to the housing. Interpreted broadly, claim 12 was found to lack novelty and the main request rejected. For this Board at least, G1/25 did not change things but simply confirmed G1/24 on the matter of claim interpretation.
What is “it”?
The Patentee’s first auxiliary request amended claim 12 to require “fixing a heater assembly comprising at least one heater element to the open end of the housing so that it extends across the opening of the housing”. Including the “fixing” feature restored novelty. The Opponent cited a problem with the pronoun “it”, saying that it was ambiguous.
The Board of Appeal agreed that “the term “it” in claim 12 was indeed unclear. Grammatically, “it” as used on the claim was found to be a possible reference either to the heater assembly or to the heater element” (r. 27). Both readings made technical sense, in the view of the Board of Appeal, and both were considered compatible with the description. Consulting the description was therefore considered of no help. It was found that the application as filed disclosed the heater element extending across the opening, but not the heater assembly as a whole.
An unresolved ambiguity is a broader claim
Neither party had asked for a stay pending G 1/26. The Board of Appeal therefore went ahead to assess whether the ambiguity added matter. The Board first rejected the two-step approach of T 367/20 and T 847/24, which it considered appeared to require that any ambiguity must first be resolved by interpretation before compliance with Article 123(2) EPC can be assessed. For the Board of Appeal in the present case, such an approach implies that, in case of ambiguities, a claim must be interpreted in such a way that no violation of Article 123(2) EPC arises, an approach it resoundingly rejected: “compliance with Article 123(2) EPC cannot be a precondition for the correct claim interpretation, but must instead be assessed after that interpretation has been established” (r. 31).
The Board of Appeal, however, also chose not to treat an unresolved ambiguity as leaving the interpretation “open”. Rather, the Board of Appeal considered, “an unresolved ambiguity may simply result in a broader interpretation” (r. 32). The Board of Appeal in this case therefore gave a clear “yes” to Question 3(a) of G1/26. For this Board of Appeal, where the meaning of the claim is ambiguous, the claim is considered to cover all of them.
Claim 12 was thus read as if it said that “[the heater assembly or the heater element]” extends across the opening (r. 33). One of these alternative interpretations of the claims was found to lack basis and the claim therefore to add matter. In other words, a unsolved ambiguity should be construed as claiming both alternatives. This approach fits with the guidance to examiner’s on how to apply G1/24.
The Patentee was able to rescue the patent by deleting the method claims at the oral proceedings. The Board of Appeal admitted this late request under Article 13(2) RPBA, as the ambiguity objection had only been raised at the hearing. The product claims were found novel, and the case was remitted to the Opposition Division for inventive step.
Analysis
In this case, the Board of Appeal found that if a reading of the claim in consultation of the description leads to two possible interpretations, the claim must be considered to cover both and both interpretations must have basis. This is a serious risk of patentees in conjunction with the EPO’s added matter rule. Interestingly, whilst lack of clarity is not a ground of opposition, added matter very much is. Ambiguity leading to added matter therefore seems a way that opponents may bring a clarity objection at opposition via the back-door.
The decision also suggests the circumstances where amending the description can leave you in a worse position post-grant from an added matter perspective. In this case, the patentee had a problem with added matter. However, this was not an inescapable trap because the ambiguity in the claims was left unresolved (and so any post-grant amendment to resolve the ambiguity would be narrowing). An ambiguous claim covering “A or B” is broad. Limiting to either A or B would be narrowing and Art 123(3) does not become a problem. The fatal case is the one where the description is amended in line with the claims in a way that inadvertently is aligned to subject matter that was not in the application as filed (e.g. by narrowing a broader definition leading to an intermediate generalisation). By this reasoning, a vague description is survivable by narrowing amendment, whilst a clarified, consistent and adapted description may leave you in an inescapable added matter trap.
We now have to wait to see if the EBA will agree with the Board of Appeal in this case.
Author: Rose Hughes
Rose is a biotech and pharmaceutical patent specialist with over a decade of experience in intellectual property. Rose is a patent attorney at Evolve, where she leverages our unique fractional in-house model to provide clients with deep patent law expertise combined with the strategic commercial oversight typically associated with senior in-house counsel.
With a PhD in Immunology from UCL, Rose applies her technical background to complex innovations in biologics, cell and gene therapies, and the rapidly emerging field of AI-assisted drug development. Previously, Rose held the role of Director. Patents at AstraZeneca, where she was responsible for global IP portfolios and IP strategy at every stage of the pharmaceutical pipeline, from platform development and on-market commercialization to SPCs and patent term extensions.
A recognized thought leader in the field, Rose has been a regular contributor to IPKat since 2018, offering practical insights into European patent law developments. She is also a frequent speaker on the epi podcast, a guest lecturer for the Brunel University IP law Postgrad Certificate, and a contributing author to published books A User’s Guide to Intellectual Property in Life Sciences (2021) and Developments and Directions in Intellectual Property Law (2023).
