1.1 General principles 

Subject to the next sentence, no person may be compelled to be represented by a professional representative in proceedings before the EPO; this holds for all parties to such proceedings, e.g. applicants, proprietors, opponents. A party (natural or legal person) who has neither residence nor principal place of business in a contracting state must be represented by a professional representative; the party must act through a professional representative in all proceedings, other than in filing the application (which includes all acts leading to the assignment of a date of filing) or initiating the European phase within the applicable time limit (see E‑IX, 2.3.1). To "be represented" is to be interpreted as meaning due representation, including not only notice of the appointment of a professional representative but also, where applicable, the filing of authorisations of the appointed representative (see A‑VIII, 1.6).

Parties having their residence or principal place of business in a contracting state may also act directly before the EPO, even if they have appointed a professional representative (see A‑VIII, 1.2), an employee (see A‑VIII, 1.3) or a legal practitioner (see A‑VIII, 1.5) to act on their behalf. When conflicting instructions are received from parties and their representative, each will be advised of the other's action.

Should opponents who are party to the proceedings and do not have either residence or principal place of business within the territory of one of the contracting states fail to meet the requirement set out under Art. 133(2) in the course of the opposition procedure (e.g. the representative withdraws from the opposition case or the appointed representative is deleted from the list of professional representatives), they are requested to appoint a new representative. Irrespective of whether they do so, the EPO will nevertheless inform opponents of the date and location of any oral proceedings and draw to their attention that if they appear only by themselves they are not entitled to act before the division.