5.1.1 Principles

The extent to which amendments may be admissible in opposition proceedings was discussed in T 1149/97 (OJ 2000, 259). Once a decision to grant has been issued, the European examination procedure is closed and its results become binding on the applicant and the EPO in that no further amendments may be made. However, if an opposition is filed, the patent in suit may be amended. Such amendments are not left to the general discretion of the patent proprietor, since opposition proceedings are not a continuation of the examination proceedings (G 1/84, OJ 1985, 299). However, the patent proprietor may, pursuant to R. 80 EPC (R. 57a EPC 1973) – without prejudice to R. 138 EPC (R. 87 EPC 1973) – react to the opponent's objections by amending the description, claims and drawings, provided that the amendments are occasioned by the grounds for opposition specified in Art. 100 EPC, even if the respective ground has not been invoked by the opponent (see also in this chapter IV.C.5.1.2). In addition, amendments occasioned by national rights of earlier date are admissible pursuant to R. 138 EPC (see also in this chapter IV.C.5.1.3).

According to the board in T 1149/97, those regulations could be seen to reflect the formal aspects of a procedural cut-off effect associated with the grant of a patent in the opposition phase. The grant of a patent did not constitute a general cut-off point in that the patent had to be defended in unamended form. However, only amendments as reactions to actual or possible grounds of opposition or to conflicting earlier national rights were admissible (R. 80 and 138 EPC). Possible substantive cut-off effects for amendments after grant could, in the board's view, only be based on Art. 123(3) EPC (see also chapter II.E.2.3.2).

Since the EPC does not provide for surrender of the patent in opposition proceedings, patent proprietors can merely request that the patent be amended. In requesting that the patent be maintained in a limited form, a patent proprietor is merely attempting to delimit it against objections raised by the EPO or the opponents, and does not, by virtue of such limitation, irrevocably surrender subject-matter not covered by the request as limited. In principle, the patent proprietor is free to withdraw such a request at any time during opposition proceedings or to amend it subsequently and, in particular, to resume a defence of the patent as granted, unless this would constitute an abuse of procedural law or the proprietor is prevented from doing so by the prohibition of reformatio in peius (see e.g. T 123/85, OJ 1989, 336; T 296/87, OJ 1990, 195; T 445/97; T 473/99; T 699/00; T 880/01; T 794/02; T 934/02; T 1018/02; T 1213/05; T 1394/05; T 1150/11; T 385/15 and T 43/16, which refer to this principle as established case law).

Unlike R. 137(3) EPC (R. 86(3) EPC 1973), R. 80 EPC (R. 57a EPC 1973) does not specify the point in time up to which the proprietor may amend the description, claims and drawings under the requirements specified in this provision. The boards had from the beginning based their decisions on the principle that the proprietor has no right to have amendments admitted at any stage of opposition proceedings and this did not change by the introduction of R. 57a EPC 1973. The discretion of the opposition division with regard to late-filed amendments was however derived from different provisions of the EPC (including R. 116(2) and Art. 114(2) EPC). In R 6/19 the Enlarged Board of Appeal held that Art. 123(1) EPC is the basis for the EPO's discretion whether or not to admit claim requests in opposition proceedings (see also T 966/17, which cited Art. 123(1), first sentence, EPC, read together with R. 79(1) and 81(3) EPC, and T 256/19, which referred to R 6/19 and T 966/17 and cited Art. 123(1) EPC in conjunction with R. 79(1) EPC and/or R. 81(3) EPC and, in the case of arranged oral proceedings, with R. 116(2) EPC). In T 754/16 the board emphasised that for the opposition division to have discretion not to admit new requests, these had to be late filed in the first place. For details regarding the late submission of amendments in opposition proceedings, see in this chapter IV.C.5.1.4.

In T 966/17 the board made it clear that parties to adversarial proceedings were not entitled to "detailed guidance" from the decision-making department on how to overcome a deficiency at issue. Instead it was incumbent on each party to react adequately to the submissions of the opposing party.

In G 1/10 (OJ 2013, 194), the Enlarged Board of Appeal held that R. 140 EPC is not available for correcting patents, including during opposition or limitation proceedings. However, it is always open to a patent proprietor to seek to amend his patent during opposition or limitation proceedings and such an amendment could remove a perceived error. Such an amendment would have to satisfy all the legal requirements for amendments including those of Art. 123 EPC (see also full summary of G 1/10 in chapter III.L.2.1.; but see also T 657/11, summarised in chapter IV.C.5.1.8).