A Board of Appeal (BoA) at the EPO has referred new questions to the Enlarged Board of Appeal (EBA) on broadly two issues: (1) the role of the description in interpreting patent claims, both generally and when assessing added matter under Article 123(2) EPC; and (2) the admissibility threshold for referrals to the EBA.
The referral arises from case T 0873/24, an opposition appeal concerning ArcelorMittal’s European patent for coated steel strips (EP 3587104). The dispute centred on whether the claimed titanium-to-nitrogen ratio being “in excess of 3.42” - which does specify units - introduces added matter over the application as filed, where the ratio was explicitly defined as a weight ratio. The opponent (POSCO) argued that omitting the units generalises the claim to cover, for example, a molar ratio, which was never disclosed. The patent proprietor countered that the description makes clear that only a weight ratio was intended.
The Board identified three divergent approaches in post-G 1/24 case law regarding the extent to which the description may influence claim interpretation when assessing added matter:
- (i) consulting the description only to identify the skilled person and their common general knowledge, leaving all technically sensible interpretations of the claim open;
- (ii) using the description to exclude interpretations incompatible with the technical context of the patent, without reading additional features from the description into the claim; and
- (iii) adopting a holistic approach, treating claim interpretation as a unitary exercise in which the claims are read together with the description.
Crucially, the Board’s view is that application of the first two approaches to the present case would lead to a finding of added matter, whereas the third would not. The outcome, therefore, turns directly on which interpretative approach should be adopted.
The EBA’s decision will likely affect patentees and opponents alike, regardless of the outcome. If the first or second approach prevails, claim drafting discipline will become ever more critical, as the description may not be available to rescue inadequate claim language. Existing granted patents with similar ambiguities, such as undefined units or implicit parameters, would become more vulnerable. If the third approach prevails, the drafting of patent descriptions would gain ever more importance.
Separately, the Board questioned the prevailing strict view (as expressed in T 116/18) that a referral is only admissible once a Board has ruled out all other grounds of opposition. It argued that this sets the bar too high and undermines the EBA’s harmonising function, a concern that is particularly acute now that the Unified Patent Court (UPC) also applies the EPC. The Board noted that the UPC’s involvement increases the risk of divergent interpretations, making the EBA’s role in ensuring uniformity even more important.
The substantive questions once again go to the heart of claim interpretation of European patent claims. We await the EBA’s answers with interest as they will, no doubt, further influence how practitioners draft and amend claims.
