Where the European patent is transferred during opposition proceedings the new patent proprietor entered in the Register of Patents takes the place of the previous patent proprietor both in the opposition and in the appeal proceedings. His entitlement may not be questioned in these proceedings (T 553/90, OJ 1993, 666).
For a transferee of a patent to be entitled to appeal, the necessary documents establishing the transfer, the transfer application and the transfer fee pursuant to R. 22 EPC must be filed before expiry of the period for appeal under Art. 108 EPC. Later recordal of the transfer does not retroactively validate the appeal (T 656/98, OJ 2003, 385). In appeal proceedings, substitution of another party for the patent proprietor is possible only once the relevant department of first instance has made the entry in the register or where there is clear cut evidence of a transfer (J 26/95, OJ 1999, 668, T 593/04). The procedural requirements to be fulfilled for recording the transfer of a European Patent in the register (filing of a request, providing evidence, payment of a fee) need not be fulfilled at the same time. If they are met at different times, the transfer takes effect vis-à-vis the EPO from the date on which all of these requirements are fulfilled (T 128/10). The original party remains, as long as the transfer has not been proven, a party to the proceedings, with all its rights and obligations (see T 870/92 of 8 August 1997). A name change does not result in a change of legal identity (see T 19/97).
In T 15/01 (OJ 2006, 153) the board distinguished between the situation where a party acquired a patent through a transfer, as in T 656/98 and through a merger, as in the case before the board. It held that R. 20(3) EPC 1973 (now R. 22(3) EPC) did not apply in the latter case, where the change of proprietor status was caused by universal succession of law. The universal successor of a patent applicant or patentee automatically acquired party status in proceedings pending before the EPO.