The core of Rule 137(5) EPC is non-unity, not forbidding claims for unsearched subject-matter

P. de Lange (NL)


Summarizing Rule 137(5) first sentence as forbidding amended claims that relate to unsearched subject-matter, is too imprecise. The rule combines two elements, by referring to subject-matter which is both (i) unsearched and (ii) lacks unity of invention with the originally claimed invention. In this article I provide an analysis of the rule's scope, discussing amongst others a subtle but important change in the Guidelines 2017 concerning Rule 137(5). I conclude that for applicants (and patent attorneys), only the "non-unity" element (ii) is of practical relevance. It turns out that the "unsearched" element (i) is primarily for use by the EPO. Furthermore, because the rule's original purpose was quite limited (and the Board's case law keeps it that way), the rule forbids claim amendments only in specific cases. In particular, the rule forbids fewer amendments than the Guidelines suggest. Finally, provided that the "non-unity" element is applied correctly, the case law of the Boards about the "unsearched" element has become overly complex.


Rule 137(5) first sentence (hereinafter: s1), stipulates that amended claims "may not relate to unsearched subject-matter which does not combine with the originally claimed invention or group of inventions to form a single general inventive concept." For Rule 137(5)(s1) to apply, the amended claims must relate to subject-matter that is both (i) unsearched and (ii) lacks unity of invention[1] with the "originally claimed invention or group of inventions". Each of these two elements individually specifies a case wherein amended claims are allowable. Hence, under Rule 137(5)(s1), claim amendments are allowed if (i) they relate to searched subject-matter or (ii) have the unity of invention (or both). Of course, even if a claim amendment is allowed under Rule 137(5) first sentence, the amendment can still be forbidden under the second sentence of Rule 137(5), or e.g. under Article 123(2) EPC.[2]

In this article, I will discuss two main difficulties of interpreting the rule, namely the meaning of "unsearched" and "originally claimed invention or group of inventions". The requirement of "unity of invention" is of course difficult in its own right. However, this substantive requirement is exactly the same under Rule 137(5)(s1) and Article 82. It is also of a more technical nature than the mentioned two difficulties. Therefore, I will not discuss it in this article.[3] I will simply assume that the amended claim relates either to the same invention (unity of invention present) or to a different invention (no unity of invention) compared to an original claim.[4]

The root cause for these two difficulties in making sense of the rule is the history of the rule. Rule 137(5)(s1) was added to the EPC in 1995 to repair a deficiency in the then still recent decision G 2/92. However, not every patent attorney and Examiner may still know the latter decision by heart. Accordingly, I will start my analysis of the purpose (and scope) of the rule with G 2/92.

The purpose of Rule 137(5) first sentence

The starting point of Rule 137(5)(s1) is G 2/92. G 2/92 was the result of a referral by the President of the EPO. The referral was about the case wherein an application is filed with claims for inventions A and B, and the applicant does not pay the additional search fee for invention B, when invited to do so under Rule 64(1). The EPC then does not explicitly provide for any consequences during examination. The referral asked essentially whether the applicant can have the application examined in such a case if he restricts the claims to the unsearched invention B only.[5] The Enlarged Board decided in G 2/92 that this was not possible and held that "an applicant who fails to pay the further search fees for a non-unitary application when requested to do so by the Search Division [pursuant to Rule 64(1) EPC 2000] cannot pursue that application for the subject-matter in respect of which no search fees have been paid."

The holding of G 2/92 is hence restricted to cases wherein an invitation to pay additional search fees was issued. G 2/92 therefore does not apply in cases wherein the invention B is not in the claims as filed (e.g. all claims as filed are for invention A) and the application is amended (after receiving the search report) by dropping the existing claims and replacing them by claims for invention B taken from the description. This would provide an easy way to circumvent G 2/92. Precisely to address this possible way to circumvent G 2/92, the EPO introduced Rule 86(4) EPC 1973, now Rule 137(5)(s1).[6]

Rule 137(5)(s1) was intended to complement G 2/92, not to replace it.[7] Accordingly, Rule 137(5)(s1) does not cover the cases that are already dealt with by G 2/92. Hence, Rule 137(5)(s1) is not the legal basis for objecting to claims, if the objection is based on the non-payment of a requested additional search fee. This is confirmed by established case law (Case Law of the Boards of Appeal 2016 (CLBA) IV.B.5.3.1, T 1285/11, r. 2; T 442/11, r. 2.2.4) and is followed in the Guidelines paragraph H-II 7.2 where G 2/92 is discussed.[8] Hence, Rule 137(5)(s1) provides an addition to G 2/92, with the somewhat unfortunate circumstance that G 2/92 was never codified. Accordingly, Rule 137(5) is in fact incomplete.

From the above follows that Rule 137(5)(s1) is intended to cover only subject-matter taken from the description.[9] Nevertheless, the wording of the rule does not refer to the description. I will therefore first show that the effect of the rule is precisely so, because the rule refers to unity of invention with "the originally claimed invention or group of inventions". The reasons are as follows.

Non-unity in Rule 137(5) first sentence

As said, Rule 137(5)(s1) allows amended claims if they have unity of invention with the "originally claimed invention or group of inventions". Unity with one of the original claims is sufficient.[10] This is so even if the original claims relate to multiple inventions, because each original claim is part of the "originally claimed group of inventions".[11] Since any original claim has unity of invention at least with itself, Rule 137(5)(s1) applies only to subject-matter taken from the description. Furthermore, an amended claim based on subject-matter taken from the description is still allowed under Rule 137(5)(s1) if it has unity of invention with any of the original claims. In this way, the wording of the rule is fully in line with the rule's purpose to complement G 2/92.

Rule 137(5)(s1) refers to the "originally claimed" invention(s), not to the inventions that are searched. This makes sense, because as discussed Rule 137(5)(s1) is not intended to give effect to a restriction of the search under Rule 64 EPC (which is what G 2/92 does) or under Rules 62a and 63 EPC (which is the purpose of the second sentence of Rule 137(5) EPC).[12] Therefore, unity of invention with any of the original claims is sufficient, irrespective of whether that claim was searched.

In view of the above, the Guidelines are incorrect when referring to subject-matter which "does not combine with the originally claimed and searched invention" (GL H-II 6.2, emphasis added).[13] In the same vein the Guidelines are imprecise when stating that Rule 137(5)(s1) "should be construed as permitting any limitation of searched subject-matter which is unitary with the originally claimed subject-matter" (GL H-II 6.2, emphasis added). In case of an amended claim which is based on a claim which was not searched under Rule 64, G 2/92 applies, not Rule 137(5)(s1).[14]

The Guidelines 2017 about Rule 137(5) first sentence: important changes

However, the Guidelines were changed in the 2017 update by adding a paragraph. This new fourth paragraph of GL H-II 6.2 is a great improvement and provides a rather accurate yet concise statement of how Rule 137(5)(s1) is to be applied.

The new fourth paragraph of GL H-II 6.2 reads:

"[In] order to assess whether or not amended claims fulfil the requirements of Rule 137(5), first sentence, the examining division needs to establish first whether or not the subject-matter to which they relate has or should have been searched (see B-III, 3.5) and second whether or not an objection of lack of unity would have been raised if the amended claims had been present in the set of claims on file at the time of the search." (GL H-II 6.2)

An important change is that this new paragraph refers to the "claims on file at the time of the search". Two things can be noted. First, any claims excluded from the search (e.g. under Rule 64) are still "on file" at the time of the search. Second, the paragraph refers to the claims at the time of the search and not to the claims as filed, while Rule 137(5)(s1) refers to "originally claimed" inventions. I will first discuss why the Guidelines are correct in this, especially for Euro-PCT applications. Thereafter, I will the discuss the other element of Rule 137(5)(s1), namely "unsearched".

Relevant claims for Euro-PCT applications

Rule 137(5)(s1) refers to the "originally claimed" invention. However, the rule intends to ensure payment of appropriate search fees to the EPO. Hence, in case of a Euro-PCT application for which a supplementary European search is carried out, the claims as pending at the time of the supplementary European search under Rule 164(1) are relevant. These may already have been amended during the international phase (Article 19 and 34 PCT), under Rule 159(1) and/or under Rule 161.

For Euro-PCT applications wherein the EPO was the International Searching Authority (ISA),[15] the claims on file at the time of the "search" are relevant, but this can still refer to the international search and to any search incident under Rule 164(2) EPC. Because the EPO can issue an invitation to pay an additional search fee at either stage, and because G 2/92 applies equally to non-payment of a requested additional search fee at either stage (GL H-II 7.2, T 129/14), unity of invention with one of the claims on file at the time of either search should in my opinion be sufficient. This is also consistent with the fact that Rule 137(5)(s1) does not apply to amendments made prior to any search incident under Rule 164(2) EPC (GL H-II 6.2, last paragraph).

An example of Rule 137(5) for Euro-PCT applications

The result is that Rule 137(5)(s1) should not always be applied as it wording suggests. An example with a Euro-PCT application can illustrate this. Consider for instance a Euro-PCT application with the USPTO as ISA and with claims as filed directed to invention A. The application is amended with the response under Rule 161 EPC to have only one claim for an invention B taken from the description. If the applicant reverses after the supplementary ESR to the claims for invention A, i.e. the claims as filed and as searched by the ISA, this must still be objected to under Rule 137(5) because the claims as filed are not the "originally claimed invention" in the sense of Rule 137(5)(s1). Moreover, the claims as filed are "unsearched" in the sense of Rule 137(5)(s1) even though the were searched by the USPTO as ISA.

This brings me to the second topic to be discussed: the interpretation of "unsearched" in the case law of the Boards and in the Guidelines.

What does "unsearched" mean in Rule 137(5)?

The Guidelines rephrase the "unsearched" element of Rule 137(5)(s1) as a check whether the subject-matter of the amended claims "has or should have been searched" (GL H-II 6.2). The alternative "should have been searched" is an addition compared to the wording of Rule 137(5)(s1) and makes the application of the rule more applicant-friendly. Before discussing whether this addition is necessary, it is important that recall that the "non-unity" element already makes that Rule 137(5)(s1) only forbids amendments that involve a switch to an invention taken from the description. Hence, the "unsearched" element must have a function of allowing such a switch in some cases. Frankly, allowing such a switch is exceptionally applicant-friendly and indeed it is allowed only in exceptional cases. Namely in the cases wherein an Examiner has generously searched for prior art not only for the claimed invention(s), but also for a further invention only described in the description. If later the claims are directed to that searched invention from the description, this must be allowed under Rule 137(5)(s1).[16] The "unsearched" element furthermore gives freedom to Examiners to allow an amended claim if they know that they have carried out a search its subject-matter, irrespective of whether the amendments involves a switch to an invention taken from the description or not.[17]

No need for additional consideration of "should have been searched"

According to the Guidelines, amended claims are also allowed if the amended claims "should have been searched". This is in line with established case law (CLBA IV.B.5.3.2). The addition is however superfluous. In particular, claims that the "unity" element of Rule 137(5)(s1) and claims that "should have been searched" are the same. This is so, because in the context of Rule 137(5)(s1), the phrase "should have been searched" can only relate to the question to what extent the Examiner must search for prior art not only for the claims but also for embodiments in the description. For the "should have been searched", the Guidelines refer to GL B-III 3.5, where it is said the search should cover the subject-matter to which the claims might reasonably be expected to be directed after amendment. This is based on Article 92 EPC, which provides that the search report shall be drawn up "with due regard to the description" (GL B-III, 3.1). However, this criterion begs the question what "reasonably expected" amendments are. In my view, these are amendments that relate to the same invention as the subject-matter claimed at the time of search. On the other hand, an amendment involving a switch to a different invention taken from the description can not be said to be reasonably expected. However, this is precisely the same distinction as set by the "unity" element of Rule 137(5)(s1) between allowable and non-allowable amendments. Therefore, the additional allowed case of amendments relating to subject-matter that "should have been searched" as mentioned in GL H-II 6.2 and CLBA IV.B.5.3.2, is superfluous, because it is already covered by the "unity" element of the rule.[18]

The above analysis of the "non-unity" element does not mean that Examiners must carry out a search of (all) the embodiments in the description that relate to the claimed invention(s) already when drawing up the search report. They can also do so later, when amended claims are filed that directed to such embodiments, namely as additional search during examination.[19]

From the above, it follows that the "unsearched" element of Rule 137(5)(s1) can be understood as simply an applicant-friendly exception providing that in case the EPO carries out a search for an invention only described in the description (without being required to do so), the claims can later be directed to that searched invention.[20] This primarily enables the EPO to allow amended claims under Rule 137(5)(s1). However, the applicant can also invoke the element, if the record shows that the invention in the description was actually searched[21], e.g. in the search opinion or in the "Information on Search Strategy" sheet.[22]

Hence, Rule 137(5)(s1) can be summarized as forbidding amendments involving a switch to inventions that are taken from the description and that were hence not in the claims pending at the time of search by the EPO (the "non-unity" element), unless the EPO has actually carried out a search those inventions in the description (the "unsearched" element).

A difficult case: one broad claim with many embodiments in description

Rule 137(5)(s1) as summarized above can however be easily circumvented by filing an application with a single broad claim 1 and many embodiments in the description.[23] The embodiments lack unity of invention with each other. Depending on the circumstances of the case, the embodiments may however very well have unity of invention with claim 1. Can the claims then be amended to each of these embodiments? T 736/14 can possibly be used to prevent this. Therein the Board held that that for one application (and one examination fee), only one invention is to be examined.24 Hence, after the applicant has amended the broad claim and directed it to a first embodiment taken from the description, he can no longer switch to a second or further embodiment taken from the description under T 736/14.


Rule 137(5)(s1) can be summarized as forbidding amendments directing claims to inventions that are taken from the description and that were not in the claim set pending at the time of search by the EPO (the "non-unity" element of the rule), unless the EPO has actually searched those inventions in the description (the "unsearched" element). Even though the "non-unity" element of the rule does not refer to subject-matter taken from the description, the interpretation follows from the clear and limited purpose of Rule 137(5)(s1) to prevent circumvention of G 2/92 by putting inventions in the description rather than in the claims (OJ 1995, p. 420). The two elements are also linked: the "non-unity" element implicitly specifies to what extent the EPO is required to search the description (under Article 92). The "unsearched" element allows applicants to benefit from the case that the EPO searched inventions in the description without being required to do so. It also enables the EPO to allow amended claims if sufficient prior art is on file.

Finally, Rule 137(5)(s1) is merely an addition to G 2/92. Hence, currently only the addition is codified in the Rules. The holding of G 2/92 is (still) not. Possibly Rule 137(5)(s1) could be amended in due time to codify G 2/92 (and improve clarity as well). Until that time, the fourth paragraph of GL H-II 6.2 (added in 2017) provides an accurate statement of how the rule is to be applied. However, although the reference to subject-matter which "has or should have been searched" therein accurately reflects current case law, the alternative of "should have been searched" is superfluous.

  1. Rule 137(5)(s1) uses the same phrase "to form a single general inventive concept" as Article 82.
  2. This article focuses on the first sentence of Rule 137(5) and in this way complements the article of Robin et al. in epi Information 2012(2), p. 44-47 which discusses Rule 137(5) in general. See also the presentation of E. Weinberg and Y. Robin for Examination Matters 2017, available at, with useful references to the case law.
  3. The interested reader is referred to the article of Robin et al. in in epi Information 2012(2), p. 44-47.
  4. Article 82 EPC in fact refers to a "group of invention so linked as to form a single general inventive concept". I will treat such a group of inventions as one invention in this article.
  5. The claims directed to invention B only can of course not be refused under Article 82 EPC.
  6. Notice of the EPO about the new rule in OJ 1995, p. 420, §2. According to T 708/00, r.5-7 (OJ 2004, p. 160), rule 137(5)(s1) must be interpreted "in a manner favourable to the applicant" and in line with the rule's purpose as given in that Notice. See also T 274/03, r. 4 and 5.
  7. See e.g. T 708/00, r. 7.
  8. GL H-II 7.2 "Rule 137(5) cannot be invoked. It does not apply when the applicant has not paid the [additional search fee]." GL H-II 6.2 about Rule 137(5)(s1) on the other hand does not contain an explicit statement of this important limitation of the rule; it is only said that the situation "is different" from that discussed in H-II 7.2.
  9. Hence, the paragraph of the Guidelines (H-II 6.2) discussing Rule 137(5), first sentence, is correctly titled "Subject-matter taken from the description".
  10. T 708/00, hn. 1 and r. 8
  11. There is a difference in use of the term "group of inventions" in Rule 137(5)(s1) and Article 82. Article 82 allows a patent application to relate "a group of inventions so linked as to form a single general inventive concept", i.e. to one inventive concept. Rule 137(5)(s1) does not require such a link between the inventions of the group of inventions. That a group of inventions can be multiple inventions is also clear from T 0129/14, r. 5.1.
  12. T 333/10, r. 3.7 seems incorrect in referring to lack of unity of invention with the claims as searched. However, the underlying case was unusual already from the analysis of Art. 82 in the search report.
  13. The same applies for GL B-II 4.2.
  14. Similarly, if the amended claim is based on a claim not searched under Rule 62a or 63, the second sentence of Rule 137(5) applies rather than
  15. I disregard the other cases wherein no supplementary European search report is drawn up (GL B-II 4.3.1). the first sentence. See OJ EPO 2009, 533, pt. 7.4.
  16. By analogy, there is no legal basis for the Examining Division requesting an additional search fee if it considers that Search Division failed to note a lack of unity of invention. On the other hand, correctness of an invitation to pay a search fee is to be reviewed by the Examining Division, see e.g. T 631/97 followed in e.g. J 3/09, T 1285/11, T 2248/12 and T 0129/14. In the same way, Rule 137(5)(s2) applies only if the subject-matter is not searched in accordance with Rule 62a or Rule 63, i.e. does not apply if the restriction of the search was based on incorrect application of these rules.
  17. Rule 137(5)(s1) is not a rule giving a discretionary power to Examiners, unlike Rule
  18. None of the decisions cited in CLBA IV.B.5.3.2 as supporting the addition of "should have been searched" is convincing. T 2334/11 and T 345/13 refer to GL B-III 3.5, which leaves open the question what amendments can be reasonably expected. In T 789/07, the requirement of unity of invention was also complied with, making the analysis of "unsearched" obiter dicta.
  19. See e.g. T 264/09 wherein the Board admitted the amendment but left open whether an additional search was necessary and remitted the case to the Examining Division.
  20. This exception may apply equally to optional features in claims. Furthermore, even if an optional feature is not actually searched, an amendment to make it mandatory can not be objected to under Rule 137(5)(s1) if the feature relates to the same invention as the claimed subject-matter. See also Y. Robin, epi Information, 2016(4), p. 39-41.
  21. There is a difference between the search and the search report. The search report (e.g. Form 1503) only refers to the claims, but an Examiner can still search for prior art for embodiments in the description.
  22. OJ 2017, A106.
  23. This scenario is also discussed in GL B-III 3.5.