If a party consists of a plurality of persons, an appeal against a decision which adversely affects this party has to be filed on behalf of all these persons through their duly determined common representative (see G 3/99, OJ 2002, 347, where multiple opponents file a joint opposition; T 1154/06, with respect to joint proprietors of a European patent; see also R 18/09, with respect to joint proprietors and a petition for review) (T 755/09).

In G 3/99 (OJ 2002, 347), the Enlarged Board of Appeal held that where the opposing party consisted of a plurality of persons, an appeal had to be filed by the common representative under R. 100 EPC 1973. Where the appeal was filed by a non-entitled person, the board of appeal was to consider it not to be duly signed and consequently invite the common representative to sign it within a given time limit. The non-entitled person who filed the appeal should be informed of this invitation. If the previous common representative was no longer participating in the proceedings, a new common representative should be determined pursuant to R. 100 EPC 1973 (see also R 18/09).

In order to safeguard the rights of the patent proprietor and in the interests of procedural efficiency, it had to be clear throughout the procedure who belonged to the group of common opponents or common appellants. If either a common opponent or appellant (including the common representative) intended to withdraw from the proceedings, the EPO had to be notified accordingly by the common representative or by a new common representative determined under R. 100(1) EPC 1973 in order for the withdrawal to take effect (see e. g. T 562/13).

Where an appeal is filed by only one of several joint members of a party and where this member is not the common representative, the board of appeal should send the common representative a communication giving him the opportunity to fulfil the necessary requirements of the EPC (see G 3/99, T 1154/06). If the common representative does not do so, the notice of appeal is deemed not to have been filed. Such an appeal is thus treated in the same way as an appeal filed but not signed by an authorised person (R 18/09; see also T 755/09).

In T 755/09 the appeal was filed only on behalf of one of several persons who, at the time of filing the appeal, were the joint applicants of the application in suit (see Art. 59 EPC). In principle the appeal had therefore to be held inadmissible in accordance with R. 101(1) EPC. The board pointed out that the case did not come under the category calling for a communication under R. 101(2) EPC inviting the appellant to remedy deficiencies under R. 99(1)(a) EPC within a specified period (see G 1/12, OJ 2014, A114). The notice of appeal was unambiguous nor did the appellant ever claim that the notice of appeal contained a deficiency under R. 101(2) EPC. The legal remedy foreseen in R. 101(2) EPC therefore could not apply (see also T 656/98, OJ 2003, 385).