Under Art. 123(1) EPC, a European patent application or a European patent may be amended in proceedings before the EPO, in accordance with the Implementing Regulations. R. 137(3) EPC is of particular relevance.

R. 137(3) EPC stipulates that no further amendment may be made without the consent of the examining division. Thus the applicant may amend only if the examiner consents to the amendments proposed. Giving the examining division this discretion is intended to ensure that the examination procedure is brought to a conclusion in as few actions as possible (Guidelines C‑IV, 3; H‑II, 2.3 – November 2018 version). In exercising its discretion the examining division must consider all relevant factors; in particular, it must balance the applicant's interest in obtaining a patent which is legally valid and the EPO's interest in bringing the examination procedure to a close in an effective way (in accordance with the principles set out in G 7/93). Furthermore, the exercise of discretion under R. 137(3) EPC needs to be reasoned.

In giving or withholding such consent, the examining division has to exercise its discretion responsibly and in accordance with the principles as set out in G 7/93 (OJ 1994, 775) which, although made in relation to amendments made in the pre-grant stage, are of general validity. The Enlarged Board pointed out that in the exercise of its discretion under R. 86(3) EPC 1973 (now R. 137(3) EPC), an examining division is required to consider all relevant factors which arise in a case. In particular, it must consider both the applicant's interest in obtaining a patent which is legally valid in all of the designated states, and the EPO's interest in bringing the examination procedure to a close by the issue of a decision to grant the patent, and must balance these interests against one another (T 1982/07). Once an examining division has exercised such discretion, a board of appeal should only overrule it if it comes to the conclusion either that the examining division did not exercise its discretion in accordance with the right principles or that it exercised its discretion in an unreasonable way and had thus exceeded the proper limit of its discretion (see T 237/96 with particular reference to G 7/93, OJ 1994, 775; T 182/88, OJ 1990, 287; see also T 937/09, T 1214/09, T 918/14).

In T 1074/10 the board noted that the convergence criterion (i.e. whether the respective versions of the sets of claims converge or diverge) had been accepted by the boards of appeal and has also been applied by the boards themselves (see e.g. T 240/04, T 1685/07, T 1969/08). R. 86(3) EPC 1973 – and, equivalently, R. 137(3) EPC – leaves open entirely how the examining division should exercise its discretion and in particular, neither defines a convergence criterion nor a criterion based on prima facie compliance with the requirements of the EPC. The board was of the opinion that the "divergence" of a request from earlier requests in the sense that it changes substantially the issues at stake could be contrary to the EPO's interest in bringing the procedure to a close. Therefore, the board agreed with the cited jurisprudence and considered that divergence of a request is one factor amongst others which a deciding instance may consider when exercising its discretion under R. 86(3) EPC 1973. The decision of the examining division not to admit a request was therefore not wrong merely because this criterion was used.

In T 996/12 the board stated that, in general terms, the way in which the examining division should exercise its discretion to allow amendment of an application depends upon the circumstances of each individual case and on the stage of the pre-grant procedure which the application has reached. The board noted that the applicable Guidelines did not support the concept of converging claim sets being a requirement for allowing amendments or, conversely, a diverging claim set not being acceptable. The examining division referred to two board of appeal decisions, T 1685/07 and T 745/03, for this criterion. Apart from the fact that these decisions apply particularly to the situation where a patent proprietor submits a plurality of auxiliary requests in addition to a main request in opposition appeal proceedings, it needed to be stressed that its underlining justification was to be found in the efficiency of these appeal proceedings, the latter being of a judicial nature in contrast to the purely administrative character of the proceedings before, for instance the examining division or the opposition division. The board found that this fundamental distinction eo ipso made the unqualified application of this criterion by the department of first instance of the EPO questionable.

In T 573/12 the board noted that, as set out in G 7/93 (OJ 1994, 775), an examining division, when considering whether to admit an amendment or not, is required to consider all relevant factors which arise in the case. In particular it must consider and balance the applicant's interest in obtaining a patent and the EPO's interest in bringing the examination procedure to a close. In the case in hand, the examining division's first communication was rather vague and assessed the invention in rather general terms, without analysing the individual features. The appellant's subsequent amendment added some features to the independent claims. In the board's judgment, this was a bona fide reaction. Additionally, it was the first amendment which was dependent on the examining division's consent and the minutes showed that the examining division could and did discuss the added features. Admitting the request would not have involved excessive or unjustified additional work. Furthermore, the Guidelines (Part C‑VI, 4.7 – April 2010 version) stated: "Regarding less extensive amendments, the examiner should adopt a reasonable approach, trying to balance fairness to the applicant against the need to avoid unnecessary delay and excessive and unjustified additional work for the EPO." Given the above circumstances, the board held that the examining division did not properly balance all relevant factors and thus could not endorse the examining division's conduct.

In T 937/09 the board held that, under R. 137(3) EPC, it was for the examining division to decide in a proper exercise of discretion whether to admit amendments to a European patent application after the first communication. In the board's view, this meant that the examining division had to admit amendments filed by the applicant together with the reply to a communication giving reasoned notice of a particular deficiency for the first time, if it could already have raised an objection to that deficiency in its first communication, and if the amendments could be regarded as an objectively suitable attempt to correct the deficiency.

In T 166/86 (OJ 1987, 372) the board held that under R. 86(3) EPC 1973, further amendments – which included the submission of a separate set of claims for a given contracting state – could only be made with the consent of the examining division (see Legal Advice No. 4/80, OJ 1980, 48). The examining division had to take the decision on whether to consent to the requested amendment after due assessment of the particular circumstances. In particular, this involved balancing the EPO's interest in the speedy completion of the proceedings against the applicant's interest in obtaining a patent which was legally valid in all the contracting states. The examining division would not be able to refuse its consent to an amendment if, for good reasons, the applicant was only at that late stage in a position to request the amendment, or if the requested amendment was obviously essential for him and to take it into account would not appreciably delay the grant procedure.

In T 229/93 the board found that in the circumstances of the case the examining division should have considered refusing to consent to the amendments pursuant to R. 86(3) EPC 1973, since the filing of such amendments after the expiry of the time limit for answering the first communication of the examining division in the form of a completely retyped description was contrary to the requirement of procedural economy (see T 113/92).

In T 951/97 (OJ 1998, 440) the board held that it is easier to secure an amendment at an earlier rather than at a later stage of the procedure. See also T 76/89, T 529/94, T 937/07. For instance, the board in T 674/17 the exercised its discretion not to admit the new main request into the proceedings, in accordance with R. 137(3) and 100(1) EPC, since the new main request (submitted only after the board had sent a communication under Art. 15(1) RPBA 2007) amounted to the presentation of a fresh case.

In case T 2324/14 the examining division had found that the auxiliary request "prima facie [did] not overcome the objections under Art. 84 EPC and Art. 83 EPC", and thus it did not give its consent under R. 137(3) EPC to it. The board noted that the EPC does not define what it means for an examining division to give or deny its consent to an amendment under R. 137(3) EPC. The boards of appeal had, however, accepted that the examining division could base its decision to deny consent to an amendment on prima facie considerations and that it could deny its consent to an amendment with prima facie deficiencies. However, the examining division had not limited its examination of the auxiliary request to prima facie considerations. In fact, the examining division had considered the auxiliary request fully, since it was able to give sufficient reasons for its conclusion that a patent could not be granted on the basis of that request. The examining division thus having considered the auxiliary request fully, the board took the view that there was no discretion left for the examining division "not to admit" it. In T 2026/15 the board confirmed these findings of T 2324/14, adding that this meant that the examining division had implicitly admitted the auxiliary request and, equivalently, had given its consent under R. 137(3) EPC.

In T 1105/96 (OJ 1998, 249) the board noted that where an examining division had indicated that a further request in the form of an amended text for the main claim of an application would be allowable, it was difficult to imagine any circumstances in which it would be lawful for the examining division to deny the admissibility of such request, in the exercise of its discretion. Certainly, in the circumstances of the case in hand, the rejection in advance of such a further auxiliary request unless all preceding requests were abandoned was an abuse of procedure, an unlawful exercise of discretion under R. 86(3) EPC 1973 and thus a substantial procedural violation.