Formal requirements for European patent applications

Formal requirements for European patent applications

Good news! You’ve filed a European patent application, and after a few rounds of correspondence, you’ve now received a letter from the European Patent Office (EPO) indicating that your claims are novel and inventive. Your patent application will now be granted, right?

Well, no, not necessarily. You’re in a good position, but there are a few more things that may need to be tidied up before the patent application goes to grant. This article explains some of those things, including the requirements to:

1. Acknowledge the background art;

2. Present the independent claims in the two-part form;

3. Provide reference signs in the claims; and

4. Amend the description to conform with the claims.

1. Acknowledging the background art

According to Rule 42(1)(b) of the European Patent Convention (EPC), the description of a patent application shall (among other things),

“Indicate the background art which, as far as is known to the applicant, can be regarded as useful to understand the invention, draw up the European search report and examine the European patent application, and, preferably, cite the documents reflecting such art.”

Accordingly, the description should mention background art (also referred to as prior art) which is relevant to the invention as claimed, especially where this background art is in the form of earlier patent applications (as discussed in the Guidelines for Examination in the EPO at F-II 4.3).

However, it may be that when the patent application was filed the applicant did not know of background art that was relevant. Indeed, this can often be argued to be the case, as the applicant would not believe they had an invention if they knew of background art which disclosed the ideas forming the subject of their patent application. Nevertheless, after the patent application has been filed and a search has been requested and paid for, the European patent office (EPO) will write to the applicant with the results of that search and will almost always have arrived at a list of background or prior art documents which they believe to be relevant.

Once a set of novel and inventive claims have been arrived at, the EPO will usually then require the description to be amended in order to indicate at least the most relevant prior art (if the description doesn’t already refer to this prior art) in order to meet the requirements of Rule 42(1)(b) EPC. In some cases, the EPO will issue an examination report to request an amendment to the description to meet this requirement. In other cases, the EPO might instead simply issue a communication to indicate that they intend to grant the patent application, including an amended version of the text for the applicant to approve, in which text this change has already been made. Generally, where the EPO asks the applicant to amend the description to indicate the prior art, this can be done with a relatively brief statement indicating the relevant disclosure (e.g. a patent number if the prior art is a previous patent) and providing a short summary of what that document discloses.

Although the wording of Rule 42(1)(b) EPC suggests that citing the relevant prior art documents is not a requirement (“…preferably, cite the documents reflecting such art”), it becomes mandatory when the EPO has indicated the prior art to be acknowledged (see T11/82, r.17, 25).

2. Presenting the independent claims in the two-part form

The EPC also specifies the required form and content of claims, stating at Rule 43(1) that,

“The claims shall define the matter for which protection is sought in terms of the technical features of the invention. Wherever appropriate, claims shall contain:

(a) a statement indicating the designation of the subject-matter of the invention and those technical features which are necessary for the definition of the claimed subject-matter but which, in combination, form part of the prior art;

(b) a characterising portion, beginning with the expression "characterised in that" or "characterised by" and specifying the technical features for which, in combination with the features stated under sub-paragraph (a), protection is sought.”

Hence granted independent claims in European patents very often appear in the so-called two-part form: A first, “pre-characterising” part before the phrase “characterised in that” or “characterised by”, which describes features which are acknowledged to be found in the prior art; and a second “characterising” part after the phrase “characterised in that” or “characterised by”, which describes features which are accepted as new and inventive over the prior art.

It is worth noting, the phrasing of Rule 43(1) EPC does not require that the claims must always be written in this form, and only requires that this be done “wherever appropriate.” As is discussed in the Guidelines for Examination in the EPO at F-IV 2.3, the EPO accepts that there are instances where the two-part form is not appropriate. For example, it may be that use of the two-part form would give a distorted or misleading picture of the invention or the prior art. It may also be inappropriate to present the claim in the two-part form

  • if the invention lies solely in the combination of known elements of equal status;
  • if the invention is a modification of a known process by omitting a substance or substituting a substance for another one; or
  • if the invention is a complex system of interrelated parts, the invention residing in changes in several of these parts or in their inter-relationships.

Alternatively, it may be the case that the artificial re-stating of the claim wording into the two-part form is unnecessary because the skilled person would already be able to see clearly which features necessary for the definition of the claimed subject-matter are known from the prior art in view of the indication of the prior art already provided in the description (as is discussed at F-IV, 2.3.2 of the Guidelines for Examination).

In addition, the two part form should not be used (as is discussed at F-IV, 2.3.1 of the Guidelines for Examination) if the only relevant prior art which contains the features which would appear in the pre-characterising part, is novelty only prior art. However, even in this case, the prior art should be clearly acknowledged in the description.

One reason to consider resisting amendment of the independent claims so that they appear in the two-part form, is that this might be seen as an agreement with the EPO Examiner that the features in the pre-characterising part are indeed found in the prior art. While this might be the case, in some instances the applicant might disagree, or might simply prefer not to admit as much. If the applicant makes the amendment themselves and a dispute arises later, then it may be difficult for the applicant to argue that they do not, in fact, agree that the prior art discloses all of the features of the pre-characterising part of their claim.

Presenting claims in the two-part form does not alter their scope or their enforceability. In some cases, where an applicant has claims that are accepted as novel and inventive, the Examining Division will issue a communication indicating an intention to grant, in which the Examiner (and not the applicant) has already amended the claims so that they appear in the two-part form. In which case, it is worth considering simply accepting the amended text in order to obtain grant (unless of course there are other amendments which are more substantive and less appropriate).

3. Providing reference signs in the claims

Rule 43(7) EPC requires that,

“Where the European patent application contains drawings including reference signs, the technical features specified in the claims shall preferably be followed by such reference signs relating to these features, placed in parentheses, if the intelligibility of the claim can thereby be increased. These reference signs shall not be construed as limiting the claim.”

The sole function of reference signs is to make the claims easier to understand (as discussed in the Guidelines for Examination at F-IV, 4.18) and it is acceptable to include a comment in the description to that effect. Accordingly, the use of reference signs does not limit the scope of the claim. The requirement to provide reference signs is generally accepted as being met if the first instance of a feature in each claim is accompanied with the reference sign, and thus it is not necessary to provide a reference sign every time the feature appears in a claim.

Although the inclusion of reference signs is expressed as being preferable, in practise this is generally treated as a requirement, and EPO Examiners may insert reference signs of their own accord (as discussed in the Guidelines for Examination at C-V, 1.1(d)). Nevertheless, the requirement to include reference signs may be lifted if the applicant convincingly argues that the claims without reference signs are intelligible and are clear within the meaning of Article 84 EPC.

In many instances, by the time novel and inventive claims have been arrived at, the claims will already have been amended to include reference signs in response to an Examination Report from the EPO. However, where several rounds of communication have taken place, the applicant might have amended a claim to include a feature from the description, in which case an appropriate reference sign may have been omitted. In any event, it will usually be necessary to include all relevant reference signs in the claims before the patent application goes to grant.

4. Conforming the description to the claims

A patent can only be granted where the claimed invention is supported by the description (as prescribed by Article 84 EPC). In addition, the claims must be interpreted in light of the description (as prescribed by Article 69(1) EPC). Therefore, and because the features which appear in the independent claims are understood to be essential to the claimed invention, the description must also make it clear that those features are essential. In other words, inconsistencies between the description and the claims must be avoided. The Guidelines for Examination (at H-V, 2.7) go so far as to instruct Examiners to issue summons to Oral Proceedings where applicants who have been asked to amend the description fail to do so.

Often, during prosecution of a patent application, the independent claims are amended to introduce limitations in the form of additional features. In which case, the description must also be amended to make it clear that these features, which it may have previously presented as optional, are in fact essential. In addition any subject matter which falls outside of the scope of the claims, for example as a result of any amendments, must be indicated to not form part of the claimed invention. This can be achieved either by adding some text to the effect that the subject matter is not part of the claimed invention, or by deleting that subject matter from the description. Although previously, this might have been achieved by replacing text along the lines of, for example, “a further aspect of the invention” with “a further aspect of the disclosure”, modifications to the Guidelines for Examination (at F-IV, 4.3(iii)) in 2021 make it clear that this is no longer acceptable. As such it is now necessary to specify where parts of the description do not fall within the claimed invention.

In addition, any subject matter which is excluded from patentability under Article 53 EPC must also be either removed or reworded so that it no longer relates to excluded subject matter or to make it clear that it does not form part of the claimed invention (as is also prescribed by the Guidelines for Examination at F-IV, 4.3(iii)). This would apply to subject matter that is contrary to “ordre public” or morality, that relates to plant or animal varieties or essentially biological processes for the production of plants or animals, or that relates to methods of treatment of the human or animal body by surgery or therapy, or diagnostic methods practised on the human or animal body.

As an aside, if the applicant would like to seek protection for subject matter which is not part of the claimed invention, but which appeared in their patent application as filed, they should consider filing a divisional application directed to that subject matter. Divisional applications must be filed before the earlier patent application is finally granted, refused, abandoned, withdrawn, or deemed to be withdrawn.


Even where claims are found to be novel and inventive, the patent application may still not meet all of the requirements of the European Patent Convention, and it is not unusual for Examiners to request additional amendments to either the claims or the description, or both. Although in many cases, making such amendments does not alter the scope of protection offered by the patent once granted, not all amendments are absolutely required in all cases and in some instances the applicant may prefer to avoid making at least some of them.

This article was prepared by European patent attorney Rebecca Douglas; if you would like to discuss any of the points raised, or anything else in relation to your intellectual property, please contact your usual Hindles attorney, or Rebecca, who will be happy to help.

Related articles