The right of parties to a fair trial is a generally recognised procedural principle under Art. 125 EPC (T 669/90), and is to be observed in all proceedings before the EPO (R 2/14 of 17 February 2015 date: 2015-02-17). The predictability and verifiability of all state actions are indispensable elements of the rule of law and respect for fundamental procedural rights (G 3/08 date: 2010-05-12, OJ 2011, 10). It is a fundamental right of the parties which has to be safeguarded, irrespective of the merits of the party's submissions. The necessity to respect it is absolute (R 3/10).

Under Art. 113(1) EPC the decisions of the EPO may only be based on grounds or evidence on which the parties concerned have had an opportunity to present their comments. The right to be heard under Art. 113(1) EPC is a fundamental principle (J 13/10) and of fundamental importance for ensuring a fair procedure between the EPO and a party to proceedings before it (J 20/85, OJ 1987, 102; G 4/92, OJ 1994, 149). It is intended to ensure that no party is caught unawares by grounds and evidence in a decision turning down a request on which that party has not had the opportunity to comment (R 2/14 date: 2015-02-17). In inter partes proceedings Art. 113(1) EPC reflects the principle that each party should have a proper opportunity to reply to the case presented by an opposing party (G 4/95).

Under Art. 113(2) EPC the EPO shall examine and decide upon the European patent application or the European patent only in the text submitted to it, or agreed, by the applicant for or proprietor of the patent. This is a fundamental procedural principle, being part of the right to be heard, such that any infringement of it, even as the result of a mistaken interpretation of a request, must, in principle, be considered to be a substantial procedural violation (T 647/93, OJ 1995, 132).

A violation of the right to be heard in first instance proceedings may constitute a fundamental deficiency under Art. 11 RPBA that justifies the remittal of the case to the department of first-instance (see chapter V.A.7.4.), as well as a substantial procedural violation under R. 103(1)(a) EPC that may, if equitable, justify the reimbursement of the appeal fee (see chapter V.A.9.5.8); see, for example, T 820/10, T 623/12, J 13/10.

A fundamental violation of Art. 113 EPC in appeal proceedings can be the basis for filing a petition for review to the Enlarged Board of Appeal (Art. 112a(2)(c) EPC; see chapter V.B.4.3.). A petition for review can also be based on the failure to arrange requested oral proceedings, and on the failure to decide on a party's request. Both of these additional grounds also reflect an aspect of the right to be heard (see chapter V.B.4.4. "Article 112a(2)(d) EPC – any other fundamental procedural defect"). The case law of the Enlarged Board of Appeal under Art. 112a EPC is primarily to be found in chapter V.B.4.3., to which the reader is also directed in order to cover all the jurisprudence in relation to the right to be heard. Decisions on the right to be heard taken by the Legal Board of Appeal and by technical boards of appeal are, on the other hand, almost exclusively dealt with in the present chapter, and only exceptionally referred to in chapter V.B.4.3. "Article 112a(2)(c) EPC – alleged fundamental violation of Article 113 EPC".

For the right to be heard in examination proceedings, see chapter IV.B.2 (in particular chapter IV.B.2.5, on the refusal of an application after a single communication and chapter IV.B.2.8, on issuing a further communication). In opposition proceedings the right to be heard is inextricably linked to the principle of equal treatment, see chapter IV.C.6.1. and, with regard to opposition appeal proceedings, chapter V.B.4.3.6; as to the opposition division's obligation to invite the parties as often as necessary to file observations, see chapter IV.C.6.2.; as to the opportunity to comment on new grounds of opposition, see chapter IV.C.3.4.6. With regard to the observance of the right to be heard in the context of the taking of evidence, see chapter III.G.3.3. The right to be heard may also play a role in the decision whether to accept late filed submissions (see chapter IV.C.4. "Late submission"). With regard to the requirement for reasoned decisions under R. 111(2) EPC, see chapter III.K.3.4.