The EPC does not contain any explicit provisions regarding the formal requirements for the transfer of opponent status. Nevertheless, the boards of appeal have consistently held that formal requirements have to be fulfilled for the opponent status to be considered as transferred (see T 960/08 with reference to case law, see also T 261/03 of 24 November 2005 date: 2005-11-24). A new opponent acquires party status as opponent and as party to the opposition appeal proceedings only upon filing documentary evidence of the legal succession with the EPO of (T 244/12).

A transfer of an opposition is something that has to be requested at the EPO together with supporting evidence before it can take effect. The effective date of the transfer of an opposition must be taken as the date when the transfer has been requested at the EPO and adequate evidence provided (T 1137/97, T 19/97, T 1421/05, T 1032/10). Pursuant to T 261/03 date: 2005-11-24 (of 24 November 2005) such a request may also be an implicit one.

Until evidence of the transfer has been provided, the original party to the proceedings continues to have the relevant rights and obligations (T 870/92 of 8 August 1997 date: 1997-08-08, T 1137/97, T 413/02). Acts performed before the relevant point in time by the former opponent are valid – provided the former opponent is still in existence and able to act; acts performed by the new opponent are invalid, and may have to be repeated once the change of parties has come to effect (T 2357/12, with reference to T 1514/06).

In case of a universal succession, however, there is necessarily and automatically a continuation of the existing legal status as opponent from the date of merger (T 6/05, see further below); in the case of universal succession, the change may – upon request and production of evidence by either party – be recorded with retro-active effect as from the effective date of the legal succession (T 2357/12).