The assumed infringer of a patent (see I, 5) may file notice of intervention in the opposition proceedings within three months of the date on which infringement proceedings were instituted against him or on which he instituted proceedings for a court ruling that he is not infringing the patent. Notice of intervention must be filed in a written reasoned statement. It is not deemed to have been filed until the opposition fee has been paid in the amount prescribed in the Rules relating to Fees under the EPC.

Intervention is permissible as long as opposition or appeal proceedings are pending. A third party can only become a party to the proceedings if a party to the proceedings in which the decision was given files an appeal pursuant to Art. 107; otherwise the decision of the Opposition Division will become final on expiry of the appeal period (see G 4/91, OJ 6/1993, 339 and G 1/94, OJ 11/1994, 787). For accelerated processing of oppositions and accelerated processing before the Boards of Appeal on request, see E-VIII, 4 and 5.