Updates to the Guidelines for Examination at the EPO

The Guidelines for Examination at the EPO (which will be referred to as “the Guidelines” in this article) elaborate on the various articles/rules of the European Patent Convention and provide practical instructions to be followed (for example, during the examination of patent applications at the EPO). 

The Guidelines are revised each year, predominantly to reflect legal and procedural updates, but also to improve the content. The vast majority of the modifications tend to be minor (for example, clarification of certain statements in response to user feedback). However, each year there are updates that affect the day-to-day practice of patent attorneys and European examiners – usually, these are in response to noteworthy decisions from the Board of Appeal.  

The new version of the Guidelines is due to enter into force on 1 March 2024. Here, we discuss some of the more notable changes. 


Historically, the EPO has taken a rather strict approach when assessing entitlement to priority – all applicants named on a priority application (or their successors in title) must be named on the subsequent application (e.g., the PCT or national application claiming priority from that first filing), and any transfer of the priority right must have taken place before the filing date of the subsequent application. 

That sounds like a relatively straightforward set of rules to follow. The fly in the ointment has been that the Boards of Appeal have considered that national law is determinative in each case, which has led to some complex situations. 

In the spotlight has been the so-called “PCT joint applicants” approach. The basic version of this “joint applicants” approach is quite well established – it essentially says that simply adding an applicant at the PCT stage does not negate the priority right, as long as the original applicant or applicants is/are also named on the PCT application.

The “PCT joint applicants” approach is quite a specific scenario, relevant mainly for US-originating applications, where the US priority application names one or more inventors as applicants (as has been common in the US), but the subsequent PCT application lists those inventors as applicants only for the US (with a corporate applicant listed for the other countries). In the past, this approach has been used to bypass the requirement to show that the corporate applicant is an appropriate successor in title.  

The argument in support of this approach has been that the applicant is among the PCT co-applicants, and therefore this satisfies the criteria for the joint applicants’ approach, even though the original applicant(s) are only listed for the US. More relevant for the present changes, however, is that the EPO has frequently been challenged on whether they should be deciding on priority entitlement at all, with parties arguing that perhaps it should be left to national courts to decide this issue. 


The above issues led to a referral to the Enlarged Board of Appeal (G 1/22 and G 2/22), who ultimately softened the stance around examination of priority entitlement (see our commentary on this decision here). This has been reflected in the most recent version of the Guidelines. 

The situation now is set out as follows: although the EPO is competent to decide on issues of priority entitlement, by default there will be a “strong rebuttable” presumption that the applicant(s) are entitled to claim priority. This has led to a shift in the burden of proof – historically, it would be up to the applicant(s) to demonstrate that they are entitled to claim priority, but now it is for the examining division, opponent or third party challenging the claim to provide evidence that the applicant(s) are not entitled to priority. 

The PCT joint applicants’ approach gets a specific shout-out – in this situation, the EPO will now consider that the addition of the extra applicant(s) implies an agreement between the applicants which will allow them to rely on the priority right, unless “substantial facts indicate otherwise”. 

It will be interesting to see how the EPO applies G 1/22 and G 2/22 going forward. Look out for further commentary from us in the coming months.

These updates will be set out in Part A-III, 6.1 of the Guidelines. 

Inventive step and the principle of free evaluation of evidence

G 2/21 was perhaps one of the most talked about Enlarged Board of Appeal referrals of 2023. 

The Enlarged Board of Appeal was asked whether post-published evidence can be taken into account for the assessment of inventive step. By “post-published evidence”, we mean evidence that has been submitted after the filing date of a patent application. This might happen during examination or opposition proceedings, for example where an applicant is asserting that a product or method has a particular technical effect. 

It isn’t always practical to wait to file a patent application until a full set of experimental data is available for a particular product (e.g. pharmaceuticals, where patent applications are often filed before carrying out clinical trials), and so the filing of post-published evidence can be very helpful in situations where a technical effect is already “plausible” from the application as filed. 

The Enlarged Board of Appeal decided that an applicant/patentee may rely on post-published evidence of a technical effect for inventive step if such a technical effect is “encompassed by the technical teaching [of the application as filed] and embodied by the same originally disclosed invention”. However, in a somewhat frustrating anti-climax, no guidance was provided on how this particular criterion should be interpreted. The Guidelines, in turn, have been updated to state the outcome of G 2/21, but provide no commentary on interpretation. It’s likely that ongoing case law will help to define this further – no doubt we will see further clarification in the Guidelines in future years. 

Perhaps a clearer outcome of G 2/21 concerned the type of evidence that can be taken into account for the assessment of inventive step. “Free evaluation of evidence” means that there are no strict rules governing which types of evidence are, or are not, convincing – in other words, the more important aspect is whether or not the department in question is actually convinced of the truth of the allegation (i.e., how credible the department considers the piece of evidence to be). The Guidelines have now been updated to state that “any evidence submitted to prove a technical effect that can be taken into account for the assessment of inventive step is assessed in accordance with the free evaluation of evidence. Such evidence may not be disregarded solely on the ground that it is post-published”. 

These updates will be set out in G-VII, 5.2 and G-VII, 11 of the Guidelines. 

Sequence listings

In July 2022, a new standard for sequence listings (ST.26) came into force. European applications filed after 1 July 2022 and which require an accompanying sequence listing must include an ST.26 sequence listing.

On the face of it, this seems simple. However, WIPO gave national patent offices discretion over whether ST.26 applies to new divisional applications, leading to different practices depending on the jurisdiction in question. In Europe, the rule does apply to divisional applications filed on or after 1 July 2022. So, you can easily be in a situation where the parent application has been filed with an ST.25 sequence listing, but the new divisional application needs an ST.26 sequence listing. Converting from ST.25 to ST.26 has the potential to add matter, and so this issue is thornier than it first appears (i.e. swapping an ST.25 sequence listing for an ST.26 sequence listing is risky, and you may not be able to fix any subsequent added matter issues later). 

A solution to this problem has been to append the original ST.25 sequence listing to the end of the description as PDF pages so as not to lose this subject matter in case of any issues, but, where the sequence listing was very long, this led to enormous excess page fees. This was clearly not ideal. Thankfully, the EPO announced in November 2023 that they would waive the page fees associated with doing this, meaning that there is no additional cost associated with including the original ST.25 sequence listing (as PDF pages) in a divisional application.

This update will be set out in A-III, 13.2 and A-IV, 5 of the Guidelines. 


For those of you working in the life sciences area, the Guidelines have undergone some significant changes in recent years with regard to antibodies (in particular, inventive step of antibodies). 

One issue that plagues this technical area is that the generation of antibodies towards a known antigen is generally considered to be “routine” and well within the capability of the skilled person. Thus, if an antigen is known and there are existing antibodies that target that antigen, a further antibody that recognises that antigen will not be considered to be inventive at the EPO unless there is some sort of “surprising” technical effect. The EPO will not acknowledge inventive step simply because the antibody is structurally different compared to known antibodies. 

The Guidelines already gave some examples of what constitutes a surprising technical effect, but the list has been amended. The list now includes: “an unexpected improvement over prior art antibodies in one or more properties, such as therapeutic activity, stability or immunogenicity, or an unexpected property not exhibited by prior art antibodies”. In addition, the Guidelines now explicitly state that “a novel type of functional antibody format may also be considered inventive”. 

Notably, however, former references to “improved binding affinity”, “reduced toxicity” and “an unexpected species cross-reactivity” have been removed as examples of surprising technical effects. This likely reflects a further shift in the mentality of EPO Examiners – techniques such as affinity maturation and phage display are increasingly considered by Examiners to be “routine” and therefore an improved binding affinity may not be enough to impart inventive step. 

Elsewhere, the Guidelines also now include updated guidance on defining a claimed antibody by its epitope – something which is possible at the EPO but can present some challenges. We have recently commented on these changes here.  

These updates will be set out in Part G-II, 6.1.3 and 6.2 of the Guidelines.

Provisions relating to Artificial Intelligence/Machine Learning inventions

Artificial Intelligence/Machine Learning (AI/ML) has certainly caused a stir in recent years. In the patent world, one question that has been heavily debated in courts around the world is whether an AI system can be named as an inventor. Most jurisdictions (including the EPO) have concluded that an inventor must be a “natural person”. 

In line with the EPO’s stance, the Guidelines, which used to simply state that the EPO does not verify the accuracy of the information given regarding the inventors, now states that the EPO will check whether the designated inventor is a natural person. 

Elsewhere in the updated Guidelines, the provisions around the patentability of AI/ML inventions have been updated. To satisfy the requirements of sufficiency of disclosure, the application must describe the invention in sufficient detail that a person in the relevant technical field can put the invention into practice. For AI/ML inventions, this means that the mathematical methods or training datasets must be disclosed in sufficient detail. A similar level of data may be required to demonstrate that a technical effect is present across the full scope of the claims. 

However, in this particular technical area, it isn’t always practical or desirable to provide an entire training dataset, and there are concerns that doing so would in fact be limiting – i.e. the Examiner may require that the scope of the claims is limited to the use of that particular training dataset in the invention. In view of that, best practice is often to disclose a “suitable” training dataset, with plenty of explanation about what the data is, giving examples of publicly available data if possible. 

In line with this general approach, the Guidelines now explicitly state that, in general, there is no need to disclose the specific training dataset itself. Rather, where a technical effect is dependent on particular characteristics of the training dataset, those particular characteristics should be disclosed unless the skilled person can determine them without “undue burden using common general knowledge”.

These updates will be set out in A-III, 5.3, F-II, 3 and G-II, 3.3.1 of the Guidelines. 

Selection inventions

“Selection inventions” are those that relate to individual elements, subsets, or sub-ranges compared with known sets or ranges. The Guidelines have been updated to clarify the definition of selection inventions and how the novelty of such selection inventions is assessed, together with some practical examples. More explicit guidance is provided on how novelty is assessed depending on the number of selections compared with the prior art (i.e. one or multiple selections). 

The practical examples include a situation where a claim defines a range that is a sub-range compared with a range disclosed in the prior art, illustrating the different outcomes where the prior art does or does not disclose a concrete example within the claimed range. Other examples include an application of the “two-list principle”, where a selection from two or more lists of a “certain length” has to be made in order to arrive at the claimed combination (which will usually confer novelty unless there is a specific pointer in the prior art document). 

One notable addition is the definition of a “list of a certain length”, which is: “A list is usually considered to have a “certain length” if it has a length of at least two or three elements. Whether a list has the required length has to be decided on a case-by-case basis”. 

These updates will be set out in G-VI, 7 of the Guidelines.

Unitary Patent (UP) and Unitary Patent Court (UPC) provisions

A Unitary Patent (UP) provides the possibility of getting patent protection in up to 17 EU Member States using one single request to the EPO, rather than validating in each state individually on grant. The Unitary Patent Court (UPC) opened on 1 June 2023. For more information, see our article here. 

The Guidelines have now been updated to explicitly state the provisions around the request for a UP. In particular, a request for a UP must be filed at the EPO no later than one month following the mention of grant of the European patent in question. In addition, the Guidelines have been updated to reflect recent provisions for accelerating opposition proceedings where infringement proceedings are pending before the UPC.

These updates will be set out in Parts C-V, 2.1 and D-VIII, 1.2 of the Guidelines.