R. 100 EPC concerns the examination of appeals. If the applicant fails to reply in due time to an invitation under R. 100(2) EPC, the European patent application is deemed to be withdrawn under R. 100(3) EPC. These provisions were previously contained in Art. 110(2) and (3) EPC 1973 respectively.
The Legal Board held in J 29/94 (OJ 1998, 147), that if the appellants failed to reply in due time to an invitation under Art. 110(3) EPC 1973, the European patent application was deemed withdrawn, even if the appeal related to formal points, as the effect of the appeal, namely that the board of appeal was now competent for the case, applied to the entire application (see Chapter IV.E.1.2 "Devolutive effect of appeal").