According to R. 77(1) EPC (former R. 56(1) EPC 1973), if the opposition division notes that the notice of opposition does not comply with the provisions of R. 150(1) EPC (former R. 99(1) EPC 1973, i.e. the provisions governing, inter alia, the time limit for filing a notice of opposition), it must reject the notice of opposition as inadmissible.
In T 222/85 (OJ 1988, 128) the board stated that a communication under R. 79(1) EPC (former R. 57(1) EPC 1973) indicating the admissibility of an opposition was not a decision of the opposition division, and the sending of such a communication did not prevent the subsequent rejection of the notice of opposition as inadmissible under R. 77(1) EPC (former R. 56(1) EPC 1973), for example if the admissibility was challenged by the patent proprietor in the proceedings (see also T 621/91).
In G 1/02 (OJ 2003, 165), the Enlarged Board of Appeal examined whether a formalities officer was competent to decide on the consequences of late payment of the opposition fee and thus on the inadmissibility of an opposition. Taking the view that T 295/01 (OJ 2002, 251) and T 1062/99 were divergent, the President asked the Enlarged Board of Appeal to consider whether points 4 and 6 of the Notice of 28.04.1999 conflicted with provisions of a higher level (OJ 2002, 466). In the reasons for its decision, the Enlarged Board stated that the provisions of the Notices of the Vice-President DG 2 were valid on the basis of R. 11(3) EPC (former R. 9(3) EPC 1973), under which formalities officers could be entrusted with duties falling to the examining and opposition divisions and involving no technical or legal difficulties. It therefore concluded that points 4 and 6 of the Notice of 28.04.1999 did not conflict with provisions of a higher level.
As soon as an opposition had been rejected as inadmissible, the opposition procedure was regarded as legally terminated and substantive examination could no longer be initiated. The inadmissibility of an opposition, when finally decided, or an appeal, had the effect of transferring the European patent to the national jurisdiction of the designated states, which then assumed sole responsibility for assessing the patent's validity with reference to their own legislation. The board therefore came to the conclusion that it was inconsistent with the procedural principle referred to above for the decision rejecting the opposition as inadmissible to consider that opposition's merits. Remarks on substantive matters in a decision rejecting the opposition as inadmissible had no legal effect. However such remarks should, on principle, be avoided as a procedural deficiency of this kind could result in legal uncertainty during the national phase and could disadvantage either the proprietor or the opponent (T 925/91, OJ 1995, 469; see also T 328/87, OJ 1992, 701).