Exceptions to the principle that each party must bear its own costs may also be made in cases of abusive conduct in which it is equitable to make an award of costs against one of the parties. An apportionment of costs is often requested on the grounds that the notice of opposition or appeal has been incorrectly filed. The fact that an appeal proves clearly inadmissible does not justify an award of costs if the appellant evidently has the subjective impression that he is adversely affected. A party which is of the opinion that the first-instance department has not acceded to its request may consider that it is adversely affected by the decision and may consequently decide to file an appeal. This is no more than its legitimate right to make use of the appeal procedure provided for in the EPC and to have the decision reviewed. Occasionally having to seek defence against unfounded or even inadmissible appeals is just one of the general risks of life and thus, in the absence of any further circumstances, does not justify a different apportionment of costs. The EPC makes no distinction between successful and unsuccessful appeals for the purposes of cost apportionment; so it cannot be argued that apportionment is justified if an appeal appears to be clearly inadmissible (T 964/14, T 2177/12, T 614/89, T 772/95).

In T 170/83 the opponents had used an incorrect form for payment of the opposition fee, thereby giving rise to a decision by formalities to reject the opposition; the opponents thereupon filed an appeal against this decision. The patent proprietors (respondents) requested that the appeal costs be awarded against the appellants, since it was their error which had rendered the proceedings necessary. The board rejected the request, taking the view that the appeal proceedings were not improper. An abuse justifying the apportionment of costs could only be rooted in the party's conduct during the proceedings.

In a number of cases the boards took the admissibility or allowability of an opposition or an appeal to be an indication that no abuse had taken place (e.g. T 7/88 and T 525/88). Similarly, in T 506/89, the board found that the opponent's filing of an appeal did not constitute an abuse of procedure and therefore rejected the request for a different apportionment of costs, since it had decided, in the oral proceedings, to maintain the patent as amended. Nor was there an abuse of procedure where the appeal was filed without new arguments (T 605/92) or where the appellant's chances of success were considered to be low (T 318/91). According to T 717/95 no abuse has taken place if a party to the proceedings misinterpreted the content of a citation when comparing it with the subject-matter claimed in the disputed patent.

In J 22/12 it was disputed whether an appeal against a communication issued on behalf of the examining division could be admissible. The board found that this was not the case. It considered that the filing of an opposition and of a subsequent appeal in the matter could not be considered as an abuse of procedure as they were actions which used the provisions of the EPC for the ends envisaged by those provisions. Thus the board found it appropriate that each party should bear its own costs.