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).
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). Pursuant to T 261/03 (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, T 1137/97, T 413/02). 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).