1.5. Time limit for intervention

Under R. 89 EPC, intervention is not possible until the opposition period has expired (this was previously laid down in Art. 105 EPC 1973), but notice of it must be filed within three months of the date on which proceedings referred to in Art. 105 EPC were instituted.

If multiple proceedings are under way, the three-month time limit for intervening is always triggered by the date on which the first proceedings were instituted (T 296/93, T 1143/00).

The two alternative starting points under Art. 105(1) EPC 1973 for calculating the three-month period for intervention were mutually exclusive (T 296/93, OJ 1995, 627). See also T 144/95 and T 18/98. Article 105 EPC 1973 could not be used to give an opponent who failed to file an appeal in time a second chance, as the opponent does not fulfil the requirement of being a third party (T 1038/00).

In T 694/01 the board held that Art. 105(1), first sentence, EPC 1973 did not stipulate when infringement proceedings were deemed to have been instituted. As they could only be instituted before the national courts, the wording of Art. 105 EPC, even if not explicitly, set this date by reference to the relevant national procedural laws.

In T 452/05 the board considered three dates which could possibly have triggered the three-month period: the date on which the request for an interim injunction was made, the date on which the request was granted, or the date when the injunction order was served upon the opponent. In the board's view, only the last date should be regarded as the decisive point in time, as only from that date onwards could the opponent provide evidence of the proceedings that entitled it to intervene.

In T 691/16 the appellant (patent proprietor) disputed that the three-month time limit prescribed by Art. 105 EPC and R. 89 EPC had been adhered to since the date on the advice of delivery recording service of the notice of action was not clearly legible and, moreover, the signature on it was allegedly not identical to the intervener's. The board ruled that the intervention had been filed properly and in due time. Proving service was the very point of the advice of delivery, and both the stamped date and the handwritten date (in so far as it was legible) showed the relevant date. So there was at least prima facie evidence against which the patent proprietor had not asserted any substantiated doubts. Moreover, R. 126(2) EPC, last half of the sentence, EPC reflected a general principle whereby, in case of doubt, it was for the sender of a document, not the recipient, to prove that it had reached the recipient and when. Doubts owing to things such as illegibility therefore could not act to the recipient's detriment. As regards the differences in the signature, the board pointed out that a notice of action did not necessarily have to be served on the recipient itself, but could also be served on people living in the building or with the necessary authorisation. This was generally what happened at companies. There was therefore no reasonable doubt that the intervener's claim to have received the notice of action on the relevant date was true. It must be noted, however, that R. 126(2) EPC has been amended. See notice from the EPO of 25 November 2022 concerning legal changes to support digital transformation in the patent grant procedure (OJ 2022, A114) and of 6 March 2023 concerning amended Rules 126, 127 and 131 EPC (OJ 2023, A29). See also chapter III.D.1.

In T 308/23, the board recalled that the provisions of Art. 105 EPC were intended to allow the alleged patent infringer to defend themselves by challenging the validity of the patent within the centralised procedure before the EPO rather than through separate national proceedings. The intervention could only be initiated based on the first infringement proceedings, even if there were separate national infringement proceedings underway in different EPC contracting states. The board noted that if the alleged infringer were able to choose at will the infringement procedure allowing them to intervene in the opposition proceedings, it would be theoretically possible for them to deliberately delay the opposition proceedings by intervening at a later stage on the basis of a subsequent infringement procedure, which would run counter to the objective pursued by Art. 105 EPC and R. 89(1) EPC. Thus, the different interests of the alleged infringer in one or other of the national proceedings or its subjective assessment of the economic importance of a territory could not play a role in this context.