In J 3/87 (OJ 1989, 3) it was stated that if an EPO communication was not as clear and unambiguous as it ought to be, and led a reasonable recipient into error, that amounted to a substantial procedural violation, even if the ambiguity of the communication was partly due to an unfortunate provision of the law.

In J 17/92 the appellants complained that the examining division had used the wrong form for its communication, namely a form threatening that the application would be refused if a response was not filed. The board considered that the failure of the examining division to withdraw the wrong form and the threatened sanction of a possible refusal of the application amounted to a substantial procedural violation.