Amendments must be examined fully for compatibility with the EPC (Art. 101(3) EPC; see also in this chapter IV.C.5.2.). Thus, where the respondents (opponents) first raise an objection under Art. 100(b) EPC during the appeal proceedings to an amended claim, the appellants cannot refuse permission to discuss the new ground (T 27/95).

Where amended claims were introduced in the opposition proceedings there could be no objection to the opponent's submitting new citations and new arguments against the new claims that challenged inventive step for the first time (T 623/93). The examination by the opposition division of a new submission justified in this way was in keeping with G 9/91 (OJ 1993, 408, point 19 of the Reasons).

In T 922/94, the board recalled that Art. 102(3) EPC 1973, R. 66(1) EPC 1973 (Art. 101(3)(a), R. 82, and R. 100(1) EPC) conferred wide powers upon the boards to consider all possible objections under the EPC, pleaded or not pleaded, that might arise from an amendment of the claims originally filed. In case objections concerning the requirements of Art. 123(2) EPC were not expressly pleaded under R. 55(c) EPC 1973 (R. 76(2)(c) EPC), but formed part of the opposition division's decision, the objection under Art. 123(2) EPC formed part of the legal framework of the decision under appeal and the patentee (appellant) could not rely on G 10/91 for its request not to admit this ground into the appeal proceedings (see T 227/88, OJ 1990, 292 and T 1848/12).

In T 693/98 the board dealt with the question as to whether, on the proper interpretation of Art. 102(3) EPC, the fact that an amendment to the claims has been made in opposition proceedings opens the possibility for an opponent to raise an objection under Art. 123(2) EPC to all the amendments to the claims including those made before the patent was granted, even if such objection was not originally raised and substantiated as a ground for opposition. Citing G 10/91 (OJ 1993, 420, point 19 of the reasons) the board concluded that only the amendments made during opposition or appeal proceedings, not those made before grant, must be examined for compliance with the requirements of the EPC (see also T 301/87, OJ 1990, 335).

The introduction of a feature into an independent claim, which feature was present in the claims and in the description as granted, could not be considered as an amendment which legitimated the admittance of Art. 100(b) EPC as a fresh ground of opposition, which required that a European patent as a whole had to disclose the invention in a manner sufficiently clear and complete for it to be carried out by a person skilled in the art (T 1053/05; cf. T 739/08 and T 565/13).