Art. 101(1) EPC (Art. 101(2) EPC 1973) reinforces the right to be heard laid down in Art. 113 EPC by requiring the opposition division, when examining an opposition, to invite the parties "as often as necessary" to comment, within specified periods, on its own communications or those filed by other parties. Where necessary, any communication to the proprietor of the European patent must contain a reasoned statement covering all the grounds against the maintenance of the European patent (R. 81(3) EPC; R. 58(3) EPC 1973).
Art. 101(1) EPC does not require as a rule that the grounds for not maintaining the patent invariably be set out in a communication, but only if this is "necessary". Such "necessity" can arise only in efforts to establish the facts or in view of Art. 113(1) EPC. So the opposition division must issue a communication only if it considers this necessary, e.g. to take up new substantive or legal arguments or draw attention to points still requiring clarification. R. 81(3) EPC which merely contains instructions concerning the content of any communications that may have to be issued, adds nothing to the above consideration of principle. Accordingly, the provisions of Art. 101(1) EPC and R. 81(3) EPC cannot be interpreted as meaning that the opposition division is obliged in every case to issue at least one communication before giving its decision, unless it is necessary to do so on the basis of Art. 113(1) EPC (see e.g. T 275/89, OJ 1992, 126; T 538/89, T 682/89 and T 532/91).
Not issuing at least one communication under Art. 101(2) EPC cannot in itself substantiate an allegation of infringement of the right to be heard under Art. 113 EPC (see e.g. T 774/97 and T 781/08). For example, the boards see no need under Art. 113(1) EPC for the opposition division to announce its opinion in advance in a communication or to give a further opportunity to the patentee to declare whether he is interested in a limited patent if, despite having been informed of an additional objection of the opponent, he does not react but maintains his sole request for maintenance of the patent with the amended claims (see e.g. T 165/93). Nor is it necessary under Art. 113(1) EPC to give a party a repeated opportunity to comment on the argumentation of the EPO body, so long as the decisive objection against the contested procedural action remains the same (see e.g. T 161/82, OJ 1984, 551; T 621/91).
Whilst, in opposition proceedings, the patent proprietor has a right under Art. 101(1) in conjunction with R. 79(1) EPC (Art. 101(2) EPC 1973 in conjunction with R. 57(1) EPC 1973) to file observations on the notice of opposition, it is apparent from Art. 101(1) EPC and R. 79(3) EPC that observations of the parties are only admissible in so far as, in the exercise of its discretion, the opposition division considers them "expedient". In other words, the parties should be invited to file observations and amendments only if such an invitation is "appropriate" and such observations should be limited to what is "necessary" in the light of the grounds submitted for the opposition (see T 406/86, OJ 1989, 302). It is namely in the interests of the efficient conduct of opposition proceedings that observations by parties should be properly limited to what is necessary and expedient (T 295/87, OJ 1990, 470; T 7/95).
In this context, the case law refers to the "general principles" applying to the opposition procedure (see information from the EPO, OJ 1985, 272; OJ 1989, 417; OJ 2001, 148): The EPO’s aim is to establish as rapidly as possible, in the interest of both the public and the parties to opposition proceedings, whether, and to what extent, a patent may be maintained on the basis of an opponent’s submissions. In particular the EPO seeks to achieve this by means of an efficient and streamlined procedure. At the same time, the general principles governing the procedure before the EPO and in particular the principle of the right to be heard (Art. 113(1) EPC) must be respected.