In accordance with the principle of good faith, the EPO is obliged to warn users of the European patent system of omissions or errors which could lead to a final loss of rights. A warning would always be necessary when one could be expected in all good faith (G 2/97, OJ 1999, 123). This would presuppose that the deficiency could be easily identified by the EPO and the applicant was in a position to correct the deficiency and thereby avoid the impending loss of rights (J 13/90, OJ 1994, 456). In other words, the EPO can only be expected to warn a party of a deficiency if the deficiency is readily identifiable by the EPO, and the party can still correct it within the relevant time limit (G 2/97, J 13/11).

The principle of good faith does not impose an obligation to warn a party of deficiencies within the area of the party's own responsibility (G 2/97; see in this chapter III.A.3.3.).