G 1/25: What the Enlarged Board’s Preliminary Opinion Means for Description Amendments at the EPO

A hot topic in the European patent community is whether it will be necessary in the future to adapt the description of the European patent to the amendments that are made to the claims during prosecution at the European Patent Office (EPO). A case about this has been referred to the Enlarged Board of Appeal (EBA), namely G 1/25. This referral is expected to determine how far the EPO may go in requiring applicants and patentees to adapt the description before grant of a European patent. On 11 March 2026, the EBA issued its preliminary opinion, offering the first authoritative indication of how this long‑debated issue may ultimately be resolved. Oral proceedings are scheduled for 8 May 2026, and the final decision is widely anticipated.

The referral arose from Board of Appeal decision T 697/22, a dispute concerning a hydroponics‑related invention owned by Knauf Insulation and opposed by Rockwool. The Board accepted a narrower auxiliary request but refused a late‑filed attempt to adapt the description, creating the procedural context for the referral. The questions sent to the EBA addressed whether description amendments are necessary when amended claims introduce inconsistencies, which provisions of the European Patent Convention (EPC) require such amendments, and whether the answers differ depending on whether the inconsistency appears in examination or opposition. The EPO formally confirmed the referral on 5 August 2025, explaining that, for reasons of legal certainty, examination and opposition proceedings would continue to follow the existing Guidelines, including the practice of requiring description amendments wherever the examining or opposition division considers them necessary.

In its preliminary opinion, the EBA took a clear and pragmatic approach. It stated that only two types of inconsistencies exist between the claims and the description. The first type comprises inconsistencies that do not result in any non‑compliance with the EPC. In such circumstances, no amendment of the description is required. The second type comprises inconsistencies that do lead to a breach of the EPC, and these must be corrected by adapting the description. By framing the matter in this binary way, the EBA positioned itself between two conflicting schools of thought in earlier case law: one line of decisions suggesting that virtually every inconsistency must be removed, and another line suggesting that inconsistencies do not matter at all when the claims themselves are clear. The EBA’s approach leaves no room for the latter view and simultaneously reins in overly strict approaches that demanded unnecessary textual alignment.

As to the legal basis for requiring such amendments, the EBA identified Article 84 EPC as the correct foundation. Article 84 requires claims to be clear, concise and supported by the description. The EBA made it clear that this provision can serve as a legal basis for obliging applicants to correct description passages that undermine clarity or support. In doing so, the Board expressly distanced itself from the logic of T 56/21, a decision that had argued Article 84 does not justify mandatory description amendments if the claims themselves are clear. The EBA considered this reasoning inconsistent with its earlier decision G 1/24, which affirmed that the description and drawings must always be consulted when interpreting claims. Since claim interpretation depends on what the description discloses, the EBA reasoned that the EPO may require applicants to address inconsistencies that create EPC non‑compliance.

The EBA then addressed whether examination and opposition should be treated differently. It concluded that they should not. If an inconsistency gives rise to EPC non‑compliance in one procedural setting, the same inconsistency must be treated identically in the other. This view is consistent with the EPO’s stated approach to continue applying the current Guidelines uniformly in both procedures while G 1/25 is pending.

The broader significance of G 1/25 becomes clearer when placed in the wider context of recent EPO practice. Starting in 2021, the Guidelines for Examination were tightened considerably, requiring applicants to delete or explicitly mark embodiments in the description that no longer fell within the amended claims. This trend created substantial additional work for applicants, who often faced complex drafting tasks late in prosecution. Many practitioners warned that such extensive amendments risked introducing added‑matter problems or unintentionally narrowing claim interpretation during later national court proceedings. Several decisions, including T 1989/18 and T 1444/20, questioned the legal basis for this increasingly strict approach, while others such as T 1024/18 insisted that Article 84 requires the description to be consistent with the claims throughout its entirety. These conflicting views created uncertainty that made a referral to the EBA both necessary and inevitable.

In practical terms, the EBA’s preliminary opinion suggests a more balanced future. Some practical advice:

• Until the final decision is issued, applicants and patentees should continue to amend the description wherever genuine EPC‑relevant inconsistencies exist, while avoiding unnecessary over‑editing.
• Excessive deletions or disclaimers can have harmful consequences in later litigation, especially before national courts that rely on the description to interpret the claims.
• Practitioners should also avoid making significant amendments late in appeal proceedings because, as the referring case illustrates, Boards applying RPBA 2020 may refuse to admit such changes.

The oral proceedings in G 1/25 will be held on 8 May 2026, and the case continues to attract widespread interest across Europe. Numerous amicus curiae briefs have already been filed, most arguing against mandatory description amendments during opposition or appeal on grounds ranging from lack of legal basis to inefficiency. The EBA’s final ruling will shape EPO practice for years to come and is expected to bring greater harmonisation to how description amendments are handled across examination, opposition and appeal. In its preliminary opinion, the EBA has already signalled a more measured and legally grounded approach, focusing on inconsistencies that actually matter for EPC compliance rather than imposing blanket requirements.