Joint applicants, joint proprietors of patents and more than one person giving joint notice of opposition or intervention may act only through a common representative. If the request for the grant of a European patent, the notice of opposition or the request for intervention does not name a common representative, the party first named in the relevant document will be considered to be the common representative. This representative can thus be a legal person. However, if one of the parties is obliged to appoint a professional representative this representative will be considered to be the common representative, unless the first named party in the document has appointed a professional representative. If during the course of proceedings transfer is made to more than one person, and such persons have not appointed a common representative, the preceding provisions will apply. If such application is not possible, the EPO will require such persons to appoint a common representative within two months. If this request is not complied with, the EPO will appoint the common representative.

For Rule 100 to apply, each party or his duly authorised representative must have signed the document (request for grant, notice of opposition, etc.) giving rise to his participation (see also III, 4.2.2 and IX, 3.2 and IX, 3.4). Otherwise the party cannot take part in the proceedings, nor therefore be represented by a common representative.