In J 5/94 the board made allowance for the fact that the appellant was an individual applicant who had not appointed a representative and who was neither familiar with the requirements of the Convention nor in possession of an established office organisation attuned to ensuring that procedural deadlines were met. The board pointed out that in such a case the same standards of care as those required of a professional representative or the patent department of a large firm could not be applied.
At the same time, an individual applicant was also obliged to exercise due care in the course of the procedure. Accordingly, when not using the services of a professional representative, he must himself take all possible steps to ensure that he can do, properly and punctually, whatever is required during the grant procedure to prevent any loss of rights. He is not entitled either to invoke general ignorance of the law or to leave undone anything which may reasonably be expected of him with a view to observing time limits (J 5/94, J 27/01, T 671/02, J 2/02, J 6/07, T 493/08).
With regard to re-establishment in respect of disciplinary proceedings and the European Qualifying Examination, the board ruled in D 6/82 (OJ 1983, 337) that a mistake of law, particularly one regarding the provisions on notification and calculation of time limits, did not, as a general rule, constitute grounds for re-establishment of rights. The obligation to take "all due care required by the circumstances" meant that persons engaged in proceedings before or involving the EPO had to acquaint themselves with the relevant procedural rules.
In J 23/87 the board ruled that exercising due care under Art. 122 EPC 1973 meant that an applicant, when deciding whether to pursue his application, could not rely entirely on information provided voluntarily by PCT authorities and the EPO at various stages of the procedure, and instead had to ensure that he was normally able to comply with the basic PCT and EPC 1973 time limits even if he received this information late or not at all.
In T 601/93 the appellant was not aware of the need to file a statement of grounds within the time limit. The board held that any legal error which might have led the appellant to believe that the requirement was not to be observed would exclude the application of due care, considering the unequivocal provision in Art. 108 EPC 1973.