2. Applicability of the principle of the protection of legitimate expectations

The principle of the protection of legitimate expectations applies to all procedural actions – whether formal or informal – taken by EPO employees vis-à-vis parties to proceedings (T 160/92, OJ 1995, 35; see also T 343/95; T 460/95 of 16 July 1996 date: 1996-07-16; T 428/98, OJ 2001, 494).

It applies to both ex parte and inter partes proceedings (T 923/95).

The requirements in connection with the principle of good faith to be observed by the EPO are the same vis-à-vis all parties involved in proceedings before the EPO, be they applicants, patent proprietors or opponents (T 161/96, OJ 1999, 331, see also J 12/94).

The principle of the protection of legitimate expectations also applies to acts performed by other authorities concerned in Euro-PCT proceedings during the international phase such as the US Patent Office acting as receiving Office or as International Preliminary Examining Authority (J 13/03). It applies also to the conduct of national authorities when dealing with European patent applications filed with them under Art. 75(1)(b) EPC (J 34/03). It can also apply in situations in which, while there is no erroneous information from the EPO, the outcome is the same in that a party receives erroneous information as a result of another party's actions (see T 353/18, in which the respondent had mistakenly filed differing clean and annotated versions of the claim). 

The principle of legitimate expectations only protects parties from disadvantageous procedural consequences of the omission of procedural steps, in relying on erroneous information from the EPO. It has no bearing on substantive law and cannot render patentable what otherwise would not be. This applies, in particular, when the information – even if it were wrong – was issued by a department of the EPO that was not competent to examine patentability (T 2239/15).