In T 1644/10, the EPO had published an incorrect patent specification B1 and subsequently corrected it as B9. The appellant had relied on the accuracy of the published specification B1 and consequently failed to file notice of opposition within the prescribed period. The board held that whether the protection of legitimate expectations could be applied in an inter partes procedure where there had been a failure to meet the opposition deadline was subject to a weighing-up of interests. There was no general rule that the patentee's legitimate expectation that the grant decision had become final had to be considered subordinate to the opponent's legitimate expectation that the content of the published patent specification was correct. That would run counter to the rule of equal procedural treatment of the parties. In the case in hand, the appellant could not rely on the applicability of the principle of legitimate expectations in relation to its failure to meet the opposition deadline.

In T 595/11 the appellant had enclosed a debit order for a reduced appeal fee with the notice of appeal. The board held that the time frame within which the payment of the fee needed to be checked by the EPO and the party be warned was shorter than the four years that had passed in the present case between the expiry of the time limit for filing the appeal and the time when the Office first made the appellant aware of this issue. The legitimate expectations of the appellant that the fee payment was in good order and would not be objected to, were indeed established. After weighing up the legitimate interests of all the parties the board concluded that the original error might have had serious and inequitable consequences through the Office's failure to discover it. Therefore, it was equitable that the Office' failure was made good and the error was now allowed to be remedied, as far as possible. Seeing that some adverse effect was inevitable, the board considered that the possibility of a real, but otherwise in itself not necessarily decisive setback for a party (here the non-occurrence of an immediate success) was more preferable than a certain decisive loss of all rights for another party, in particular given the fact that for a long time none of the parties did expect the latter (see also T 1037/11, T 2554/11, T 707/12).