The ongoing debate on claim interpretation continues at the European Patent Office (EPO) with a new referral to the Enlarged Board of Appeal on 3 June 2026 in the form of G1/26 (“Coated Steel Strips”). The referral explores the relationship between claims and description and follows on from related decision G1/24 and pending referral G1/25 which were also concerned with how and when the description should be used to interpret and/or amend the scope of the claims.
Background
The story begins with G1/24 which was decided in June 2025 and confirmed that:
The claims are the starting point and the basis for assessing the patentability of an invention under Articles 52 to 57 EPC. The description and drawings shall always be consulted to interpret the claims when assessing the patentability of an invention under Articles 52 to 57 EPC, and not only if the person skilled in the art finds a claim to be unclear or ambiguous when read in isolation.
Following this decision, G1/25 (“Hydroponics”) asked whether the description must be adapted to remove inconsistencies when the claims are amended during opposition and appeal proceedings, what the exact legal basis for this is and whether the same rules would apply to amendments made during examination and examination appeal proceedings. While a formal decision is still pending, the Enlarged Board’s preliminary non-binding opinion leans towards maintaining the current requirement of description adaption. The issue of description adaption and thus the outcome of G1/25 is critical, not least because, in infringement and validity proceedings, according to G1/24, the description must always be consulted to interpret the claims when considering patentability matters like novelty and inventive step.
The Questions Referred
G1/26 now seeks to clarify what G1/24 means by ‘consulted’ and whether the same principles for claim interpretation laid out for patentability also apply to added matter (questions 2 and 3). In parallel, G1/26 has also requested procedural guidance on the admissibility rules regarding the referral of questions to the Enlarged Boards (question 1). The precise wording of the questions is as follows:
1. May a decision be considered to be "required" for the purposes of Article 112(1) EPC, if the referring Board demonstrates that the point of law in question arises out of the context of the case pending before it and, in the circumstances of the proceedings, it is reasonable for the Board to examine it and decide on it next?
2. (a) Does the fact that the claims are 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 a patent from being read into the meaning of a granted claim, in particular if this leads to a restrictive reading of terms used in the claim?
(b) If the answer to question 2.(a) is no: is claim interpretation the result of both reading the claims and consulting the description and drawings as a unitary process and does the claim being the starting point and the basis for assessing the patentability rule out only those interpretations which can be derived from the patent as a whole but would clearly contradict the general technical understanding of the terms used in the claim?
3. (a) 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?
(b) If the answer to question 3.(a) is no: is 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?
Possible Outcomes
First, the Enlarged Board will have to decide if the referral itself is admissible and thus provide an answer to question 1. This is a significant issue in itself and more detailed commentary will follow this summary. If the referral is inadmissible, then we shall have to wait for another case where the outcome depends on a similar point of law.
However, if the referral is admissible, it could open up the whole referral process by allowing Boards to proactively refer queries on key points of law earlier in proceedings as well as providing significant direction on claim interpretation. An admissible referral means that the Enlarged Board will consider and pronounce on whether the same or different rules apply to claim interpretation for added matter as for patentability.
If the same rules apply and a claim term is interpreted through the lens of the description, there is potential to loosen the EPO’s strict approach to added matter with more scope for implicit disclosures to be read into claims from the description. Conversely, if the Enlarged Board decides that claim terms should be interpreted strictly on the basis of the claims alone, then, a claim could have multiple means depending on whether patentability or added matter is at issue. Theoretically, in this scenario for added matter, a term could encompasses multiple technical meanings and, under a rigid gold standard approach, could add matter if any of those linguistically possible meanings lack a "direct and unambiguous" basis in the original filing.
This theoretical situation is illustrated perfectly by the referring case T 873/24.
T 873/24
This case resulted from an appeal by both Patentee (ArcelorMittal) and Opponent (POSCO) against the decision of the Opposition Division to maintain European patent EP3587104 B1 (Coated Steel Strips) in amended form.
Granted claim 1 specified a chemical ratio between titanium and nitrogen of "in excess of 3.42" but accidentally omitted the units. The Patentee argued that, from the description, the ratio was clearly and unambiguously a weight ratio. However, the Opponent argued that, in the absence of units, the ratio must be interpreted as also including molar ratio which was not "directly and unambiguously disclosed" in the original application and thus resulted in an added matter violation.
Conclusion
G1/26 has the potential to provide a critical turning point for EPO claim interpretation, determining whether description definitions can save claims from added matter contraventions, as well as another opportunity to consider if how claims are interpreted affects the ‘gold standard’ for added matter assessment. However, this potential will only be realized if the Enlarged Board accepts the referral and this is not at all certain.