G 1/25: Enlarged Board charts a middle course on adaptation of the description

On 3 September 2026, the Enlarged Board of Appeal issued its long-awaited decision in G1/25, addressing one of the most contentious procedural issues in European patent practice: when, if ever, applicants and patent proprietors must amend the description to conform to amended claims. We previously reported the preliminary opinion here.

While the decision provides some guidance on the issue and brings the various streams of cases to a single approach. The battleground may simply shift from whether amendments are required to whether a particular inconsistency has legal significance under the EPC.

Background

For many years, EPO practice has required applicants to amend the description whenever claims were amended, particularly where embodiments remained in the specification that no longer fell within the scope of the claims. Examiners increasingly required such embodiments to be deleted, identified as comparative examples, or labelled as not forming part of the invention.

This approach was controversial because the EPC contains no express provision requiring “adaptation of the description”. While some Boards of Appeal viewed Article 84 EPC as providing an implicit legal basis for the practice, others questioned whether such a requirement existed at all.

The referral arose from opposition appeal proceedings concerning a patent owned by Knauf Insulation. The referring Board considered the amended claims allowable but identified inconsistencies between those claims and passages remaining in the description. It therefore asked the Enlarged Board whether adaptation of the description was required and, if so, what legal basis existed within the EPC for such a requirement.

The Enlarged Board's answer

The Enlarged Board rejected both extreme views.  It declined to endorse the view that any inconsistency automatically requires amendment. Equally, it rejected the proposition that adaptation is never necessary because no explicit legal basis can be found in the EPC.

Instead, the Enlarged Board held that an amendment to the description is required only where an inconsistency results in non-compliance with a substantive provision of the EPC. They clearly stated that the EPC does not require amendment “merely for the sake of formal concordance”.

The Board's core conclusion is encapsulated in point 43 of the Reasons:

“The necessity to adapt the description or any drawings is not a consequence of the existence of an inconsistency as such, but arises only where, and to the extent that, the inconsistency has legal significance because it leads to non-compliance with a requirement of the EPC.”

The Enlarged Board therefore concluded that adaptation is required where an inconsistency causes non-compliance with Articles 52 to 57, 76(1), 83, 84, 123(2) or 123(3) EPC.

What is an inconsistency?

Perhaps more importantly, the Enlarged Board adopted a relatively narrow definition of “inconsistency”.

An inconsistency exists only where a statement in the description or drawings suggests an understanding of a claim that is incompatible with the apparent meaning of that claim, and where the incompatibility cannot readily be resolved by applying the claim interpretation principles set out in G1/24.

The Board expressly stated that an inconsistency is not established merely because the description contains embodiments, examples or technical teachings that fall outside the scope of the claims.

That observation is potentially significant. One of the principal drivers of description-amendment practice has been the EPO's insistence that unclaimed embodiments be identified as lying outside the invention. The Enlarged Board appears to have rejected the proposition that the mere presence of such embodiments creates an inconsistency requiring amendment.

The influence of G 1/24

The decision is closely linked to last year's landmark decision in G1/24. In G1/24, the Enlarged Board confirmed that claims must be interpreted using a “holistic” approach in which the claims, description and drawings are read together. The description must always be consulted when interpreting claims and not merely when ambiguity exists.

G1/25 builds directly on that reasoning. The Enlarged Board took the view that many apparent discrepancies can be resolved through proper claim interpretation. Only if the skilled person would still be left with a genuinely incompatible understanding of the claim does an actionable inconsistency arise.

In practice, this means that the existence of unused embodiments or broader disclosures will not necessarily require amendment if the skilled person can readily understand the meaning of the claims when the patent is read as a whole.

What does this mean for applicants?

At first sight, applicants may welcome the decision.

Many practitioners have spent considerable time negotiating description amendments that appeared to have little substantive effect. The decision provides applicants with stronger arguments against blanket requests to label every unclaimed embodiment as “not according to the invention” or to carry out large-scale editorial revisions solely to achieve formal consistency.

However, applicants should not assume that description amendments have disappeared.  The Enlarged Board has expressly confirmed that amendments remain necessary in at least some circumstances. Where an inconsistency creates a problem under the EPC, amendment will still be required before grant or maintenance.

The practical challenge will be determining where that boundary lies.  We can expect the EPO to issue some guidance to examiners (and applicants) in due course, and this will be key in seeing how this works in practice.

New opportunities for opposition attacks?

One of the more intriguing consequences of G1/25 may be the effect on opposition practice.

Rather than ending disputes, the decision may create new ones. Opponents can be expected to argue that a remaining inconsistency gives rise to a deficiency under Article 84, Article 83 or another EPC provision. Conversely, patentees will argue that any apparent tension can be resolved through the interpretative principles of G1/24.

There may also be increased scrutiny of description amendments that are made. As several commentators have noted, once amendments become discretionary rather than routine, opponents may attack those amendments themselves, arguing that they affect claim interpretation or create other issues under the EPC.

A compromise

The Enlarged Board has adopted what is ultimately a middle ground. Those hoping for the complete abolition of description amendments will be disappointed. Equally, the decision stops short of endorsing the EPO's most stringent practices of recent years. Adaptation of the description is not an end in itself and the EPC does not require perfect alignment between claims and description in every case.

Whether G1/25 reduces the burden on applicants will depend on how examining divisions, opposition divisions and Boards of Appeal apply the decision in practice. The key question is no longer whether an inconsistency exists, but whether that inconsistency has legal significance under the EPC.

That question is likely to keep European patent practitioners busy for some time to come.