While the boards are not obliged to provide the parties in advance with all reasons for a decision in detail (see in this chapter V.B.4.3.5), Art. 113(1) EPC requires that decisions may only be based on grounds or evidence on which the parties concerned have had an opportunity to present their comments. In R 3/13 the Enlarged Board held that this implied that a party may not be taken by surprise by the reasons of a decision referring to unknown grounds or evidence (see also R 15/09, R 21/10).
In R 3/10, R 15/11 and R 16/13 the petition was allowed because of surprising reasons on which the parties had not been given an opportunity to comment (see in this chapter V.B.4.3.19). On the other hand, in R 8/17 the Enlarged Board held that the board must be able to draw its own conclusion from the discussion of the grounds put forward.