Since the main purpose of the appeal proceedings is to review the decision of the department of first instance, the boards normally refer the case back if essential questions regarding the patentability of the claimed subject-matter have not yet been examined and decided on by the department of first instance. This applies to both ex parte and inter partes proceedings.

In particular, remittal is considered by the boards in cases where a first-instance department issues a decision against a party solely upon a particular issue which is decisive for the case, and leaves other essential issues outstanding. If, following appeal proceedings, the appeal on the particular issue is allowed, the case is normally remitted to the first-instance department for consideration of the undecided issues (see e. g. T 1088/01, T 870/03, T 1019/03, T 79/04, T 1907/06, T 282/12, T 389/12).

In some ex parte cases, the boards have refrained from deciding the whole case because the examining division had not taken an appealable decision on all patentability requirements (see e.g. T 556/03, T 561/04, T 2062/08, T 2009/13). Although Art. 111(1) EPC empowers the boards to go beyond the grounds of the contested decision, that does not mean they should carry out a full examination of the application for compliance with the requirements, that being a task for the examining division. In ex parte cases too, the main purpose of proceedings before the boards is to review the contested decision (see G 10/93, OJ 1995, 172).

In the ex parte case T 153/89 the board stated that first-instance decisions should deal with all legal obstacles to patentability. Such "complete" decisions helped to streamline proceedings by obviating the need for a remittal to the department of first instance, as the board could decide on all matters already raised at first-instance without depriving the appellant of the opportunity to have them considered at two instances (see also T 33/93, T 311/94).

In T 1444/13 the board made it clear that a first-instance department should conduct as complete an examination as possible, in order to reduce the likelihood of remittal in any subsequent appeal. Thus, having regard to the clear indications provided in the first appeal and also considering that a decision revoking a patent based solely on Art. 100(c) EPC may in many cases be set aside in appeal proceedings because a new set of claims is filed, the opposition division should have examined the requirement of sufficiency of disclosure. The board decided to remit the case to the opposition division for examination of all the outstanding issues.

In T 248/85 (OJ 1986, 261), the board observed that the department of first instance had not yet fully examined the application on the basis of the problem-solution approach and held that this alone meant the contested decision had to be set aside and the case remitted to that department without any decision on its merits.

In T 274/88 the board agreed that where an irregularity has been remedied during appeal proceedings, the matter should still normally be remitted to the department of first instance. However, in this particular case, which was ex parte, the board did not remit because, after correction, the subject-matter of the application was patentable, the appellants had expressly waived their right to have the issues considered at two instances, and the examining division had already indicated that it was favourably disposed on the question of patentability.