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Opposition Strategy: Added subject matter & intermediate generalisation


Under Article 123(2) of the European Patent Convention (EPC), it is not permissible to add subject matter to an application after is filed, while under Article 123(3), any amendments that broaden the protection of a patent after grant are to be refused.

Subject matter may inadvertently be added to an application in any number of ways, such as by adding a more detailed definition of the inventive concept to the claims, using different words to define the inventive concept compared with those originally used in the application, deleting features from the definition of the inventive concept that were presented originally as being necessary, or simply by using a definition of the invention that is somewhere between very broad or very specific examples given in the original application. This latter case is known as an intermediate generalisation and is discussed in more detail below.

The European Patent Office (EPO) takes the prohibition against added subject very seriously, and during proceedings, objections based on a ground of added subject matter are typically the first to be considered by the Opposition Division or Appeal Board, before other considerations like sufficiency (under Article 83), and finally Patentability (under Article 52, and including novelty and inventive step for example) are heard. The order in which the grounds for Opposition are heard at proceedings is often the reverse of the order in which they are presented in Article 100 EPC, based on the practical consideration that if patent claims do not meet the EPO’s formal requirements for added subject matter and sufficiency, there is little need to review them in detail against the prior art.

Strategy as Opponent

In view of the above, nearly all Opponents use arguments of added subject matter as part of their opposition strategy, even if the actual facts of the case suggest that subject matter has not really been added. An Opponent can easily prepare such an attack by conducting a linguistic analysis of the application and granted patent documents, and arguing that any change to the wording of the claims, between the filing date and the date of grant, has resulted in added subject matter. The fact that not all such arguments are convincing often does not always deter an Opponent from at least trying the approach.  

It is relatively straight forward and inexpensive for an Opponent to present arguments of this kind. However, for the Patentee it can be costly, since the structure of Opposition and Appeal Proceedings generally requires the Patentee to present their whole case (including arguments and amended claims) at the earliest opportunity. Thus, the Patentee may find themselves having to respond to each and every added subject matter argument offered by the Opponent, even if they disagree with those arguments, or believe that they have little merit. The difficulty for the Patentee is not knowing which of the Opponent’s added subject matter arguments will be considered valid.

Although added matter objections can be raised with relative ease, it is not always in an Opponent’s interest to raise them just for the sake of it.  Reviewing added matter objections can can take up a considerable amount of time at a hearing and because such objections tend to be dealt with first, valuable time may be wasted at a hearing discussing these peripheral arguments.  This has the knock-on effect that the more substantive issues like novelty, sufficiency and inventive step are rushed through at the end of the day.  It is not uncommon to see a party who thinks a rushed discussion of inventive step will be in their favour, dragging out the discussion on added matter to use up as much time as possible. 

This situation could be improved for both the Opponent and Patentee by more direct case management from the EPO. At present, the EPO offers a minimal indication of the merits of the case, only in the Summons to Oral proceedings before the Opposition Division or Appeal Board. This issues at quite a late stage, often after both the Opponent and Patentee have exchanged at least one full round of correspondence and argument. Further, the indication in the summons often goes no further than indicating which arguments or attacks appear the strongest and will be considered at the proceedings. As a result, both Opponent and Patentee may find themselves throwing their full weight of argumentation at the case, right up to the day of the proceedings, with little to indicate what the EPO consider to be the real issues. This is not ideal for the Opponent, the Patentee or indeed the EPO.

Strategy as Patentee

In view of the above, the challenge for the Patentee is to pick though any added subject matter arguments from the Opponent, and make a decision about those that appear problematic. After all, Patentees usually do not intentionally add subject matter to their application, and it can be unclear, even when presented with an argument from an Opponent, whether there is in fact a problem. Essentially, the Patentee is put in the position of trying to determine whether the Opposition Division or Appeal Board will agree with the Opponent’s added subject matter objections, at an early stage in the proceedings, whether the Patentee agrees with them or not.

The Patentee has a number of options for dealing with this. Although it is not necessary that amendments to claims (made during examination or Opposition) use the exact wording of the application as originally filed – either in the description or claims – it can be preferable if they do, thereby sidestepping any allegation that subject matter has been added by the use of different wording, and avoiding a long or complicated discussion during Opposition or Appeal.

During examination and before grant, European applicants may therefore wish to make only minimal amendments to the claims, to deal with the specific objections raised by the European examiner. Further, they may wish to avoid making amendments that were used to deal with objections in overseas patent offices, where added subject matter requirements and the allowability of amendments are treated differently.

If possible, amendments based on dependent claims may be preferable to amendments based on the description or drawings. After grant, amendments that are based on dependent claims cannot be argued to introduce a lack of clarity to the claims, whereas amendments based on the description can be argued to both introduce a lack of clarity, and even to constitute an unallowable intermediate generalisation compared with the original disclosure.

At the drafting stage, use of multiple claim dependencies in the dependent claims, makes later amendments simpler, as it can avoid the argument that subject matter has been added by an amendment presenting dependent claim features in combinations that were not originally disclosed.

Arguments Against Added Subject Matter Objections – the Gold Standard

Of course, it may not always be possible or desirable to use the exact wording of the original description or claims for a claim amendment, and despite the discussion above, it is not a requirement of the EPC that amendments use the exact or verbatim wording of the original application. It just makes things simpler if they do, by avoiding the need for lengthy argument or discussion.

Amendments for which there is not verbatim or exact language in the description or claims are to be assessed using the EPO’s self-designated “Gold Standard”. This states that amendments can “only be made:

a) within the limits of what a skilled person,

b) would derive directly and unambiguously,

c) using common general knowledge, and

d) seen objectively and relative to the date of filing,

e) from the whole of these documents as filed”.

Read in full here.

The effect of the Gold Standard is to provide a framework in which added subject matter allegations and the permissibility of amendments can be objectively considered. Further, the references to the ‘common general knowledge of the skilled person’, and the ‘whole of the document as filed’ emphasise that the test for added subject matter is whether the skilled person is presented with information that was not in the application as originally filed, not merely that different wording has been used. The Gold Standard is nevertheless to be interpreted narrowly, as basis for the amendment must still be ‘directly and unambiguously’ derivable from the original application.

Arguments Against Added Subject Matter Objections – Intermediate Generalisation

An intermediate generalisation can arise when the Patentee amends an initially very broad claim, to a more specific example or embodiment described in the description, without taking all of the associated relevant detail of that example or embodiment into the claim. This is termed an intermediate generalisation, as the final amended claim scope lies somewhere between the very broad or very specific examples originally disclosed, without the original application necessarily presenting that scope of claim as part of the invention.

Intermediate generalisation issues can be avoided at the drafting stage by making it clear which features of the invention are optional, and what alternative features might be. Where features are presented as specific to an embodiment, it can also be helpful also to explain how such features can be generalised to work with other embodiments.

An Opponent will often raise an intermediate generalisation objections if an amendment is based on an embodiment in which a number of features are presented together, but the Patentee has omitted one or more of those features in the final amended claim. As explained in the Guidelines to the EPC “the content of the application as filed must not be considered to be a reservoir from which individual features pertaining to separate embodiments can be combined in order to artificially create a particular combination”. Making sure that the description of the invention avoids such allegations is therefore much of the challenge. However, if there is any doubt, the Patentee will need to argue against the objection.

In order to do so, it must be clear that any features of the embodiment omitted from the amended claim language would not be considered a key part of the implementation of the invention. Again, the guidelines state that “extracting a specific feature in isolation from an originally disclosed combination of features and using it to delimit claimed subject-matter may be allowed only if there is no structural and functional relationship between the features”. Put more fully, a Patentee needing to argue against an allegation that there has been an intermediate generalisation, will need to establish that:

“the [omitted] feature is not related or inextricably linked to the other features of that embodiment and

the overall disclosure justifies the generalising isolation of the feature and its introduction into the claim”.

While this in fine in principle, there remains some uncertainty or variation on how to interpret “not related or inextricably linked”.


Opponents and Patentees may view Oppositions and Appeals at the EPO as a forum primarily to discuss the novelty and inventive step of the claimed invention. While that is true, more formalistic requirements like added subject matter can often present equally significant challenges to the validity of European patent. While the Patentee can avoid many added subject matter problems at the drafting stage, or by exercising care while amending during examination, they are still likely to face added subject matter attacks raised by an Opponent.

Considerations for the Patentee

The following considerations may assist in avoiding added subject matter problems during Opposition or Appeal:

  • Base amendments on the exact wording of the description where possible.
  • Only amend the claims to respond to objections put forward by the EPO, and where possible make the smallest number of amendments actually needed.
  • Ensure that the dependent claims provide useful amendments, thereby minimising the need for later amendments that are based on the description.
  • Use multiple dependencies in the claims where possible in order to avoid allegations that a new combination of features has been added to the application by amendment.
  • Ensure that the description of embodiments of the invention include discussion of alternative features, and how features of different embodiments may be combined.

This article is for general information only. Its content is not a statement of the law on any subject and does not constitute advice. Please contact Reddie & Grose LLP for advice before taking any action in reliance on it.

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