According to the case law of the boards of appeal, the principle of the protection of legitimate expectations governing procedure between the EPO and applicants requires that communications addressed to applicants must be clear and unambiguous, i.e. drafted in such a way as to rule out misunderstandings on the part of a reasonable addressee. A communication from the EPO containing erroneous information which misleads the applicant into taking action causing the refusal of his patent application is null and void in its entirety (J 2/87, OJ 1988, 330). An applicant must not suffer a disadvantage as a result of having relied on a misleading communication (J 3/87, OJ 1989, 3; J 23/14). On the contrary, if his actions were based on a misleading communication he is to be treated as if he has satisfied the legal requirements (J 1/89, OJ 1992, 17).

In T 2092/13 the board concluded that a communication from the examining division was ambiguous and had misled the appellant. In the circumstances of the case, the communication had created a realistic and reasonable expectation that any subsequent negative finding on the issue of novelty and/or inventive step was communicated to the appellant before any adverse decision would be taken. The appealed decision was set aside and the case remitted for further prosecution. See also T 1423/13.

The Legal Board suggested in J 17/04 that it was the EPO's responsibility to provide forms which catered for all procedural possibilities in a clear and unambiguous manner. In the case in hand the applicant was allowed to rely on a possible interpretation of the text of the EPO form in accordance with the principle of the protection of legitimate expectations even if another interpretation was more current.