24/06/2026
There has been a further referral to the Enlarged Board of the European Patent Office requesting clarification on matters of claim interpretation. This is referral G1/26 from the Technical Board of Appeal T0873/24 in connection with European patent EP3587104B.
This is now the third case in a series of cases (such as G1/24 “claim interpretation” decision and G/25 “description amendments”) which investigate the proper relationship between the claims of the European patent and the description, and how that relationship might affect claim interpretation for questions like clarity, added subject matter, and novelty.
Issues Arising in G1/26
The referral in G1/26 concerns European patent EP3587104B directed to a “pre-coated steel strip”. Claim 1 of the patent defines the composition of the steel, and contains a list of steel components expressed as weight percentages.
The claims of the application were amended during examination to additionally define a “ratio of titanium to nitrogen in excess of 3.42”. The amendment had originally been made in 2021 during examination of the application and as part of a second Auxiliary Request. Third party observations had been filed against the pending claims of the original application, and the 2021 response was an attempt to overcome the third party prior art and the EPO Examiner objections.
The original dependent claims and application discussed this ratio only in terms of a “weight %”, and the amendment made to claims during examination omitted the limitation that the ratio was based on a weight percentage. The second auxiliary request was presented by the applicant as incorporating the wording of the original dependent claims, yet failed to use the exact claim wording.
The patent has since been opposed. The opponent argued that since the ratio had not been limited to a weight percentage the defined ratio between titanium and nitrogen could be read to including other mass fraction ratios such as atomic percent, volume fraction, or molar fraction. This would constitute added subject matter in the granted claim.
The patentee argued in reply that the rest of the claim wording refers to “weight ratios” and that it was clear, despite the missing wording, that the ratio of titanium to nitrogen should also be considered a “weight ratio “even if not expressly defined as such. The patentee also argued that the skilled person would understand that such ratios are usually expressed as weight percentage ratios so that the meaning of the claim was clear and no subject matter had been added.
Questions for referral
The referring Technical Board of Appeal in T0873/24 agreed that the disputed wording of the claim is problematic, and appear to have rejected the patentee’s arguments that the expression in the claim should necessarily be interpreted as meaning “weight ratio”.
The earlier Enlarged Board of Appeal Decision in G1/24 considered how, for patentability purposes, the claims should be interpreted based on the description, and decided that “the description and any drawings are always referred to when interpretating the claims, and not just in case of unclarity or ambiguity”. Our detailed discussion of the case can be found here.
The Technical Board of Appeal in T0873/24 has asked the Enlarged Board to consider similar questions for deciding questions of added subject matter. Questions 2a and 3a for example are particularly relevant
2a) “Does the fact that the starting point and the basis for assessing the patentability of an invention generally preclude a feature which is only disclosed in the description or the drawings of patent from being read into the meaning of a granted claim, in particular if this leads to a restrictive reading of the terms used in the claim?”
3a) “When assessing compliance with Article 123(2) EPC, must a term used in a claim be assessed against all interpretations that make technical sense to the skilled reader on the basis of the claim alone?”
The questions for the referral therefore focus on the correct “interpretation” of the claim for the purposes of assessing its meaning, and for assessing whether, based on the chosen claim interpretation, subject matter has been added.
Added Subject Matter at the EPO
In European practice, amendments that are “directly and unambiguously derivable” from the disclosure of the application as filed are allowable and do not add subject matter. This condition is interpreted strictly, however, and amendments that are themselves “ambiguous”, or that rely on ambiguous or indirect support in the description, are likely to be found inadmissible.
The Case law of the Boards of Appeal sets out the Gold Standard approach to assess whether an amendment is allowable. This states that amendments can only be made “within the limits of what a skilled person would derive directly and unambiguously, using common general knowledge, and seen objectively and relative to the date of filing, from the whole of these documents as filed”.
The referring Technical Appeal Board in T0873/24 note however that this approach still requires an initial interpretation of the claimed invention. In a first step, the patent claims are interpreted from the perspective of a skilled person, and in a second step, it is assessed that the subject-matter of the amended claim – established by way of interpretation – contained subject matter extending beyond the content of the application as filed. The Technical Appeal Board referred to decisions in the case law where different interpretations were followed leading to different outcomes.
Summary
The Enlarged Board of Appeal will now review the referring Technical Board of Appeals questions, and possibly reformulate them before providing further clarification.
In providing further guidance, it is hoped that the Enlarged Board of Appeal will further clarify the statement from G1/24 that the “description and any drawings are always referred to when interpreting the claims”, and comment on the correct interpretation of the claims for added subject matter considerations. Specifically, this will likely address whether it is ever appropriate to use limitations found in the description to defend against attacks of added subject matter. To this practitioner this approach seems unlikely however, in view of the existing body of case law requiring solely the claim wording to be clear and to define the invention.
The decision also highlights the utmost importance of making amendments during examination that have direct and unambiguous basis in the description, and to the extent possible use the exact wording of the original claim or the appropriate description text. Although this is not always possible, it does seem that in this case, the patentee made proceedings much more difficult for themselves by choosing different claim wording to the original dependent claim they were relying on.
Again, the case stresses the importance in applications and patents that relate to compositions of matter to be clear about how numerical ranges, proportions, and ratios are to be measured and interpreted.
This content is for general information only. Its content is not a statement of the law on any subject and does not constitute advice. Please contact Reddie & Grose LLP for advice before taking any action in reliance on it.
