In T 873/24 (Board of Appeal 3.3.05, oral proceedings 3 February 2026), the Board announced that it will refer questions to the Enlarged Board of Appeal (EBA) on whether (and how) the Enlarged Board’s claim-interpretation guidance in G 1/24 extends to the assessment of added subject-matter under Article 123(2) EPC and Article 76(1) EPC.
Background
The appeal concerns EP 3 587 104 B1, relating to aluminium-coated steel strips. The central issue is an objection under Article 100(c) EPC directed to a compositional parameter: claim 1 of the main request includes a feature that the ratio of titanium to nitrogen is “in excess of 3.42”. This ratio was taken from the description where it was indicated to be a ratio based on weight, but the basis of the ratio (weight or molar) was omitted. In its preliminary opinion, the Board held that omitting the basis of the titanium to nitrogen ratio in the claim resulted in an unallowable extension of subject-matter.
Key findings of the oral proceedings
The proprietor argued that the titanium to nitrogen ratio in claim 1 should not be interpreted in isolation but in view of the description, where it is indicated that relevant compositional quantities are expressed by weight, arguing that the skilled person would understand the ratio accordingly when reading claim 1 as granted in context.
Such an approach would be in line with G 1/24, which prescribes (in the context of patentability under Articles 52 to 57 EPC) that the description and drawings shall always be consulted to interpret the claims, not only when the claim is unclear or ambiguous when read in isolation.
In the oral proceedings, the Board considered that the outcome of the case hinges on the question whether the claim interpretation of G 1/24 should be applied to added subject-matter as well as to patentability. In other words, when assessing added subject-matter in this case, should the titanium to nitrogen ratio should be read in isolation, meaning that it could refer to ratio bases other than weight (e.g. molar), or should the ratio be interpreted in view of the description and “fixed” to the intended meaning of a weight ratio?
The Board concluded that the issue raised a point of law of fundamental importance and announced that the case would be referred to the EBA, with the questions to be formulated in writing.
Analysis and implications
If the Enlarged Board would come to the conclusion that the principles of claim interpretation of G 1/24 also extend to the assessment of added subject-matter, this would have far-reaching consequences for the “gold standard” (direct and unambiguous disclosure) that has been used for the assessment of added subject-matter since G 3/89.
