EPO clarifies when patent descriptions must be amended – key takeaways from decision G 1/25

When patent claims are amended before the European Patent Office (EPO), the description and drawings may also need to be adapted. In decision G 1/25, the Enlarged Board of Appeal clarified when such adaptation is required.

The Enlarged Board of Appeal (EBoA) delivered its decision in G 1/25 in September 2026, providing guidance on when the description/drawings of a patent or application must be adapted following claim amendments. The decision concerns both examination and opposition/opposition-appeal practice before the EPO and may significantly reduce purely formal demands for description adaptation.

The background of the case

The referral originated from opposition appeal case T 0697/22 and concerned an appeal against the opposition division’s decision to maintain the patent on the basis of an auxiliary request. The proprietor filed, for the first time, a new amended description at the oral proceedings before the Appeal Board (the Referring Board). The Referring Board considered the new amended description late-filed and did not admit it.

A summary of the decision G 1/25

1. there is an inconsistency between the amended claims and the description/drawings,
2. the inconsistency suggests an understanding of a claim which is incompatible with the apparent meaning of the claim,
3. the incompatibility cannot be readily resolved by applying the principles of established claim interpretation following G 1/24,
4. the skilled person reading the claim in the light of the description and drawings would be left in real doubt as to the meaning of the claim, and
5. the inconsistency causes non-compliance with one or more of Articles 52 to 57, 76(1), 83, 84, 123(2) or 123(3) EPC.

The Enlarged Board of Appeal also clarified that the EPC does not require adapting the description merely for the sake of formal concordance with the claims.

A key question is what is an “inconsistency”. The EBoA stated that a description is not inconsistent merely because it contains examples or embodiments that fall outside the scope of the claims. An inconsistency arises only when the skilled person would be left in real doubt as to whether particular teachings, examples or embodiments are covered by the claim.

An inconsistency between claims and description matters only if it leads to non-compliance with a requirement of the EPC.

When should the description be amended?

The Enlarged Board of Appeal issued obiter remarks as to when the claims should be amended. The EBoA stated that in appeal proceedings the description (incl. drawings) is almost always finalised in the oral proceedings before the Board.

The EBoA concludes that where adaptation of the description is needed, it should generally be finalised during oral proceedings rather than via remittal to the first instance (that could result in a further appeal). As this is an obiter remark, it remains to be seen whether the Technical Boards of Appeal will follow this recommendation.

Practical implications

For practitioners, G 1/25 offers a stronger basis for resisting generic requests to “bring the description into conformity”. Examiners and Opposition Divisions may now be expected to identify the specific EPC provision allegedly offended by the inconsistency rather than relying on a general requirement for tidiness.

However, resisting an amendment causes additional communication and costs. Thus, one must decide on a case-by-case basis whether to resist an amendment. Currently, the EPO seems to take a more relaxed approach by not automatically requiring amendment of the description when the claims are amended.

Note also that the EBoA stated that the same principle of inconsistency applies even when the claims have not been amended. An opponent could raise the issue in opposition even if the claims were not amended during prosecution, if an inconsistency exists between the originally filed description and claims.

Further, a positive signal to applicants/proprietors, is that the EBoA indicated that where adaptation is required, it will generally be preferable to finalise it during appeal proceedings, particularly during oral proceedings, rather than remitting the case to the first instance. Hopefully, the Boards of Appeal will follow this recommendation. Such an approach is more cost-effective for applicants/proprietors. Having to file an amended description together with each auxiliary request would add costs compared with amending the description only for the specific claim set eventually accepted.