In numerous decisions the boards have ruled on the "all due care required by the circumstances" issue. In considering it, the circumstances of each case must be looked at as a whole (T 287/84, OJ 1985, 333). The obligation to exercise due care must be considered in the light of the situation as it stood before the time limit expired. In other words, the steps the party took to comply with the time limit are to be assessed solely on the basis of the circumstances applying at that time (see e.g. T 667/92, T 381/93, T 743/05, J 1/07, T 1465/07, J 3/12, J 4/12). The requirements of re-establishment, and in particular of due care, must not be interpreted in an excessive manner that unreasonably restricts access to the board and thus prevents the board from deciding on the merits of the case (T 1465/07).
In T 30/90 the board held that the allowability of applications for re-establishment hinged on whether the conduct of the appellant and/or his representative, during the entire period after the relevant decision, was indicative of "all due care required by the circumstances". In this connection, "all due care" meant all appropriate care, i.e. as much as would be taken under the circumstances by the average reasonably competent patentee/representative (see also J 11/09). The board in T 1289/10 held that as a general rule, a representative acting reasonably would at least take account of known problems and apply known solutions to avoid them.
For cases where the cause of non-compliance with a time limit involves some error in the carrying out of the party's intention to comply with the time limit, the case law has established the criterion that due care is considered to have been taken if non-compliance with the time limit results either from exceptional circumstances or from an isolated mistake within a normally satisfactory monitoring system (J 2/86, J 3/86, OJ 1987, 362; T 428/98, OJ 2001, 494 and T 785/01). In the latter case, the relevant party must show that the system normally works well (see e.g. J 9/86, J 27/88, J 28/92, T 27/86, T 166/87, T 715/91, T 612/90, T 731/91, T 179/92, T 371/92, OJ 1995, 324; T 377/93, T 956/93, T 681/95, T 1062/96, T 186/97, T 428/98, OJ 2001, 494 and T 785/01).