Under R. 88(1) EPC (R. 63(1) EPC 1973) the decision on apportionment of costs in opposition proceedings may consider only the expenses necessary to ensure proper protection of the rights involved (T 167/84, OJ 1987, 369; T 117/86, OJ 1989, 401; T 416/87, OJ 1990, 415; T 323/89, OJ 1992, 169). The order for apportionment of costs should be such as to compensate the other party for the unnecessary costs which it has incurred as the direct result of the appellant's failure in its duty (T 212/07, T 952/00). On the costs of interpreting at oral proceedings, see chapter III.C.8.2.

According to Art. 16 RPBA (2007), the costs ordered to be paid in appeal proceedings may be all or part of those incurred by the receiving party and may inter alia be expressed as a percentage or as a specific sum. In the latter event, the board's decision is a final decision for the purposes of Art. 104(3) EPC. The costs ordered may include costs charged to a party by its professional representative, costs incurred by a party itself whether or not acting through a professional representative, and the costs of witnesses or experts paid by a party but shall be limited to costs necessarily and reasonably incurred.

Under R. 88(1), third sentence, EPC, the costs include the remuneration of the parties' representatives. In T 854/09 the board stated that the costs concerned were those reasonably incurred by the opponent. In this case, where an adjournment of oral proceedings was necessary, this included the expense of a single representative preparing for and attending the second proceedings, including travel and accommodation. Under R. 88(2), last sentence, EPC, costs may be fixed once they have been established as credible. The request must be accompanied by a bill of costs and supporting evidence. The board in T 475/07 exceptionally took the view that a detailed cost calculation was superfluous. It worked on the assumption that the representative could calculate on the basis of one day for preparing the additional oral proceedings and one day for attending them. The cost estimate of EUR 2 300 thus seemed credible.

In T 930/92 (OJ 1996, 191) the board held that, when fixing the amount of costs to be paid to a party, in addition to the remuneration of the professional representative of that party, the expenses incurred by an employee of that party in order to instruct the professional representative before and during oral proceedings could be taken into consideration under R. 63(1) EPC 1973, if such instruction was necessary to assure proper protection of the rights involved. In T 326/87 (OJ 1992, 522), all the costs incurred as a result of the remittal to the department of first instance were deemed to be apportionable.

Since the filing of new material after expiry of the opposition period may cause the other party to incur additional costs, the board, in T 117/86 (OJ 1989, 401), ordered that the appellant should pay the respondent 50% of his representative's costs in preparing and filing the response to the appeal (see also T 83/93).

In T 715/95 new documents were submitted only in the appeal proceedings, and the delay was not justified. However, the board admitted the documents, remitted the case to the department of first instance and ordered the late-filing party to bear 50% of the cost of the oral proceedings. Similarly, in T 45/98, the appellant submitted new documents only in the appeal proceedings, and they were admitted. The case was not remitted to the department of first instance, but the appellant was ordered to pay 45% of the costs incurred in the appeal proceedings by the respondent's representative.