When appeal proceedings start, responsibility for the case passes from the department of first instance to the boards of appeal (known as the devolutive effect; see T 473/91 date: 1992-04-09, OJ 1993, 630; T 830/03, T 555/08).

On appeal, the department of first instance loses its competence for the further prosecution of the application for all contracting states – the appeal does not leave a part of the application pending in the first instance. Thus, deemed withdrawal of the application pursuant to Art. 110(3) EPC 1973 applied in the case of a failure to reply to a communication pursuant to Art. 110(2) EPC 1973 in ex parte appeal proceedings, even where the decision under appeal did not refuse the application, but only a particular request. The board reasoned that even if the appealed decision concerned only the designation of a state and not the application as a whole, according to the principle of unity of the application and of the patent in the proceedings the suspensive effect of the appeal affected the application as a whole (J 29/94, OJ 1998, 147).

The devolutive effect of the appeal does not affect the competence of the department of first instance to decide on a request concerning the contents of the minutes of the oral proceedings held before it. What is devolved is the subject-matter decided by the appealed decision (T 1198/97).

According to T 1382/08, the devolutive effect of an appeal before a board extends only to that part of the impugned decision which is indicated in the statement of grounds for appeal and actually challenged by the appeal. For the board, therefore, the extent to which the impugned decision is to be amended, as defined under R. 99(2) EPC, is simultaneously the limit of the devolutive effect. This in turn implies that the impugned decision's part not covered by the statement of grounds of appeal also cannot be part of the appeal proceedings and consequently becomes final on expiry of the time limit for appeal. This approach was also adopted by the same board in T 448/09. Only those issues that were considered and decided upon in the decision can later be challenged in appeal proceedings (T 2117/11). However, the board in T 689/09 noted that, whilst it was aware of case law, according to which the distinction between different legal effects of a decision also fell under the "extent to which the impugned decision is to be amended" pursuant to R. 99(2) EPC, (T 1382/08), this approach left the notion of the "subject of the appeal" even more diffuse and elusive.

See also in this chapter V.A.3.2. "Subject-matter under examination".