It is established jurisprudence of the boards of appeal that the admissibility of the appeal is to be examined ex officio at every stage of the appeal proceedings (see T 15/01, OJ 2006, 153), and thus also at the oral proceedings (T 501/09, T 2223/10, T 198/15). It can and, where appropriate, must be raised by the board in appeal proceedings even if this is the first time this matter is addressed (T 289/91, OJ 1994, 649; T 28/93; T 522/94, OJ 1998, 421; T 1668/07).
In T 670/09, the respondent did not challenge the appeal's admissibility until two days before the oral proceedings. The board observed that, under Art. 12(2) RPBA 2007, the reply to an appeal had to contain the respondent's entire case. As a rule, respondents had to object to the appeal's admissibility or the board's competence in limine litis, i.e. before submitting their substantive defence. The respondent's objection to admissibility was therefore disregarded.