The amendment of the description in line with the claims has been a long-standing feature of patent prosecution and opposition practice at the EPO. Applicants are routinely required to amend the description to remove, reword, or disclaim parts of the description to remove any subject-matter that may imply that the patent protects embodiments which are broader than or inconsistent with the final set of allowed claims. This practice is widely regarded as a distinctive feature of European patent prosecution, as no other major patent system imposes an equivalent, systematic requirement to amend the description in this way.

In recent years, however, the legal basis for mandatory description amendments under the European Patent Convention (EPC) has been increasingly questioned, with two distinct, opposing lines of Board of Appeal case law emerging: one that supports that inconsistencies between the claims and the description must be removed before grant or maintenance of a patent, and one that holds that the EPC does not require this kind of amendment as long as the claims themselves are clear and allowable.

This divergence ultimately led to a referral to the Enlarged Board of Appeal (EBA) stemming from decision T697/22, in which the Technical Board of Appeal (TBA) presented the following three questions to the EBA to ask for clarification on whether the EPC requires adaptation of the description to the claims.

• If the claims of a European patent are amended during opposition proceedings or opposition-appeal proceedings, and the amendment introduces an inconsistency between the amended claims and the description of the patent, is it necessary, to comply with the requirements of the EPC, to adapt the description to the amended claims so as to remove the inconsistency?
• If the first question is answered in the affirmative, which requirement(s) of the EPC necessitate(s) such an adaptation?
• Would the answer to questions 1 and 2 be different if the claims of a European patent application are amended during examination proceedings or examination-appeal proceedings, and the amendment introduces an inconsistency between the amended claims and the description of the patent application?

Preliminary Opinion

On 11th March 2026, the EBA issued its preliminary opinion in G1/25. Although the preliminary opinion is short, it provides a good indication of the EBA’s current position, which appears to be leaning towards requiring conformity between the description and the claims.

Question 1

The EBA has identified two types of “inconsistencies”: those that cause non-compliance with the EPC, and those that do not. Its current position on this question appears to be that, where an inconsistency gives rise to non-compliance with the EPC, further amendments to the description are required in order to comply with the EPC. The preliminary opinion does not provide an explanation of how to determine whether or not an inconsistency gives rise to non-compliance with the EPC. However, the EBA’s comments on question 2 might imply that it currently considers non-conformity between the claims and the description to lead to non‑compliance with Article 84 EPC.

Question 2

With regard to which EPC provisions necessitate such amendments, the EBA appears to take the view that the relevant provision is simply whichever Article or Rule of the EPC is rendered non‑compliant by the inconsistency in question. The preliminary opinion then focuses predominantly on Article 84 EPC, which is a provision that states that: “The claims shall define the matter for which protection is sought. They shall be clear and concise and be supported by the description”. The EBA highlights a divergence between two lines of case law with regard to how this provision is interpreted. Overall, the EBA seems inclined to reject the line of case law embodied by T56/21, in which Article 84 EPC was considered not to impose a requirement to address unclaimed or unclear subject-matter in the description. In doing so, the EBA highlights that it views the interpretation of Article 84 EPC in T56/21 to be inconsistent with its recent decision on claim interpretation, G1/24. There, the EBA decided that the description “shall always be consulted to interpret the claims when assessing the patentability of an invention”.

Question 3

The preliminary opinion clarifies that the EBA does not consider there to be a difference between examination and opposition proceedings in the context of mandatory description amendments.

Amicus briefs and stakeholder interest

G1/25 has generated significant interest across the patent community, reflected in the number of amicus curiae briefs filed. This level of engagement is not surprising given how frequently description amendments arise in day-to-day practice, as well as their time-consuming nature and potential impact on subsequent enforcement and invalidity proceedings.

Out of the 40 amicus briefs filed in G1/25, the majority argue against mandatory description amendments and answer “no” to the first of the referred questions. Most briefs were filed by patent practitioners and their professional associations. However, there have also been briefs from household names in industry, such as Apple Inc., Bayer AG, Canon Inc., Ericsson AB, F. Hoffmann-La Roche AG and Siemens AG.

The briefs raise a mix of both legal and practical concerns. Among the main arguments against mandatory description amendments is the lack of clear legal basis for this requirement in the EPC. Furthermore, certain stakeholders argue that legal certainty is achieved through compliance with Articles 52-57 EPC during examination rather than through post-hoc description amendments. Some briefs also highlight the potential of creating unnecessary added-matter risks under Article 123(2) EPC if amendments to the description are not handled carefully, as well as the associated practical burden.

Those that support mandatory description amendments focus on the role of the description in claim interpretation, emphasising that unamended descriptions can cause legal uncertainty and may unfairly benefit the patent proprietor by allowing them to argue for a broader interpretation of the claims in subsequent enforcement proceedings.

The role of Article 84 EPC

Article 84 EPC features prominently in arguments for both sides of the discussion. Those opposing description amendments argue that, although Article 84 EPC requires the claims to be clear and supported by the description, it does not impose the same requirement in the opposite direction, and therefore the presence of unclaimed subject-matter in the description does not violate Article 84 EPC as long as it is not explicitly presented as being part of the claimed invention. On the other hand, those supporting description amendments tend to argue that the claims can only be properly supported if the description is consistent with them; with this view, inconsistencies in the description violate the support requirement of Article 84 EPC.

The role of decision G1/24

G1/24, the EBA’s recent decision on claim interpretation, is also discussed in many of the amicus briefs. Stakeholders arguing against mandatory amendments suggest that G1/24 does not impose any kind of procedural obligations. They typically suggest that G1/24 simply confirms that the description should provide context and technical background needed for claim interpretation, and caution that over-removal of technical detail may distort the interpretation of the claims. In contrast, those in support of mandatory amendments insist that inconsistencies may lead to misinterpretation of the claims, and that description amendments are required for harmonisation with G1/24.

Conclusion

The EBA’s preliminary opinion seems to be leaning in favour of maintaining the need for description amendments. However, the position is not yet final and is subject to change. Whether the EBA ultimately endorses the EPO’s current practice or decides to shift to a more flexible approach remains to be seen. Oral proceedings are scheduled to be held on 8th May 2026 and will be available to members of the public via an online livestream. A final, written decision is expected later in 2026, which will provide some much-needed clarity on the EPO’s position on mandatory description amendments.