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 request 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 date: 1997-08-08). A name change does not result in a change of legal identity (see T 19/97).

In T 1068/15 and T 1001/15 the applicant requested transfer of the patent application during pending appeal proceedings. The Legal Division did not register the alleged transfer. The board considered that it had to examine the question of party status ex officio before dealing with the substance of the case (with reference to G 2/04). In doing so it was not bound by the assessment of other departments of the EPO or by the state of the Register (with reference to T 854/12).

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.

The transfer of party status as patent proprietor must be distinguished from a "transfer" of the legal entity from one jurisdiction to another. In T 786/11 the patent proprietor had requested that the address of the "applicant (patentee)" be changed from one in the British Virgin Islands to one in Mauritius and submitted evidence that it had merely changed its address. The board held that both these jurisdictions – unlike many others – allow a legal entity to be transferred from one jurisdiction to the other without any effect on its identity. The board therefore concluded that the respondent had been "transferred" from the British Virgin Islands to Mauritius and had continued as a legal entity under Mauritian law (see also T 2330/10 and T 1458/12).