According to Art. 133(1) EPC, no person shall be compelled to be represented by a professional representative in proceedings established by the EPC. However, Art. 133(2) EPC stipulates that natural or legal persons not having either a contracting state residence or their principal place of business within the territory of one of the contracting states must be represented by a professional representative and act through him in all proceedings established by the Convention, other than in filing a European patent application. The Implementing Regulations may permit other exceptions. T 1157/01 reviews the applicable law.

As recalled in J 1/04 for instance, there is no obligation for an applicant having a principal place of business within an EPC contracting state to be represented in proceedings established by the Convention. If, however, the applicant wishes to be represented, he must authorise either an employee or a professional representative or legal practitioner.

Regarding an employee of a group of companies, T 2308/10 says that an employee of a company in such a group is not entitled to represent another company belonging to the same group. T 298/97 had already established that, there being no provision in the Implementing Regulations pursuant to Article 133(3), last sentence, EPC, the EPC did not currently allow the representation of one legal person by an employee of another economically related legal person.

In T 213/89 the Japanese inventor replied directly to the EPO with a set of revised application documents, and accompanied by a letter to his representative indicating that the revised documents had also been sent to the representative. The board noted that no confirmation by the representative was received that any of the submissions directly received from the inventor should be regarded as an official reply to an EPO action. Since persons not having a residence or their principal place of business within the territory of one of the contracting states must act through their representative in the proceedings, the said submissions received direct could not be taken into account.

In T 717/04, a letter from the appealing applicant, a natural person with an address not within the territory of one of the contracting states, was faxed to the EPO with arguments and a new set of claims to be taken into account. According to Art. 133(2) EPC 1973, since the appealing applicant's address was not within the territory of one of the contracting states, the board concluded that filing claims and arguments such as those in the appealing applicant's letter would have required professional representation. As these submissions were neither made nor endorsed by the representative, the board could not take them into account.

In T 578/14 Mr S., as a resident of New Zealand, had to act through a representative in the appeal proceedings. Therefore, the board could not take into account requests and submissions, which were made neither by the representative nor endorsed by him (T 213/89, T 717/04, and J 4/10). This did not apply to submissions which exclusively concerned the appointment or change of a representative or the filing of an authorisation or of any information that the representative's authorisation has terminated.

In J 9/13 the Receiving Section refused the European patent application pursuant to Art. 90(5) EPC, because the applicant, resident in Moscow, had not appointed a professional representative as required by Art. 133(2) EPC. The appellant (applicant) contended that Art. 133(2) EPC did not apply to residents of the Russian Federation. The Russian Federation was a party to the "Partnership and Cooperation Agreement (PCA). The board stressed that neither the European Patent Organisation nor the European Patent Office is part or member of the European Union. Therefore, neither the European Patent Organisation nor the European Patent Office are bound by the provisions of the PCA, neither of them is a "party" or "other party" pursuant to Art. 98 of the PCA. The appeal was deemed not to have been filed (R. 152(6) EPC by analogy).