2.3.4 Consequences of inadmissibility

If a notice of opposition is rejected as inadmissible, the opposition proceedings are legally terminated without a decision as to the substance of the opposition. It is inconsistent with this procedural principle for the decision rejecting the opposition as inadmissible to consider its merits (not even if the division does so ex officio under Art. 114(1) EPC, according to the board in T 956/19). Remarks on substantive matters in a decision rejecting the opposition as inadmissible, have no legal effect, and should in principle be avoided (T 925/91, OJ 1995, 469).

The inadmissibility of an opposition, when finally decided, or an appeal, has the effect of transferring the European patent to the national jurisdiction of the designated states, which then assumes sole responsibility for assessing the patent's validity with reference to their own legislation (T 925/91, OJ 1995, 469; see also T 328/87, OJ 1992, 701).

In T 1420/21, the board stated that, contrary to what the respondent claimed, a situation could not arise whereby the opponent would cease to be a party to the proceedings while opposition proceedings were under way. The board said that an opponent did not "lose their status as a party" because facts, evidence and arguments filed along with their notice of opposition in accordance with R. 76(2)(c) EPC failed to comply with that rule. In such a case, the opposition would be rejected as inadmissible and there were would be no further opposition proceedings to which the opponent and patent proprietor could be a party.