The Guidelines state (General Part, point 3 General remarks – November 2018 version): "The Guidelines cannot cover all possible occurrences and exceptions in every detail, but must be regarded as general instructions that may need to be adapted to the individual case. The application of the Guidelines to individual European patent applications or patents is the responsibility of theof the formalities officers and examiners. As a general rule, parties may expect the EPO to act in accordance with the Guidelines. … It should be noted also that the Guidelines do not constitute legal provisions. For the ultimate authority on practice in the EPO, it is necessary to refer firstly to the European Patent Convention".

In T 647/93 (OJ 1995, 132) the board stated that it was normally desirable for examining divisions to act in accordance with the Guidelines, but pointed out that these were not rules of law, so failure to follow a procedure set out in them was not in itself a substantial procedural violation (T 51/94, T 937/97).

In T 162/82 (OJ 1987, 533) and T 42/84 (OJ 1988, 251), two boards of appeal ruled on the discretionary power of examining divisions to depart from the EPO Guidelines. According to these two decisions, the Guidelines were only general instructions intended to cover normal occurrences. Thus, an examining division could depart from them provided it acted in accordance with the EPC. In reviewing the decision of an examining division, a board of appeal would wish to ensure uniform application of the law and judge whether the division had acted in accordance with the Convention, not whether it had acted in accordance with the Guidelines.

In T 500/00 the board noted that what counted was not whether the opposition division had acted in accordance with the Guidelines, but whether it had acted in accordance with the Convention.

In T 1388/10, the board observed that the Guidelines merely offered general guidance covering normal occurrences. Their application in specific individual cases was the responsibility of the examining division, which could depart from them in exceptional cases. Also, the Guidelines were not the law – unlike the EPC and its Implementing Regulations. When reviewing examining division decisions, the boards did not assess whether the division had complied with the Guidelines. Rather, they considered whether it had exercised its discretion within the limits set by the EPC and its Implementing Regulations.

In J 27/94 (OJ 1995, 831) the board stated that there might be cases in which the public had a legitimate expectation that the department of first instance would not deviate from the established case law. This might apply if the relevant case law had become enshrined in the consistent practice of the department of first instance, and in particular if this had been made known to the public in published Guidelines, Legal Advice or Notices from the EPO. In such a situation, an applicant might legitimately expect that a practice allowing or even recommending a particular way of proceeding would not be changed without appropriate advance information. In the case at issue, the Guidelines had remained unchanged, which in fact led to the reasonable expectation that the practice based on them would likewise not be changed.

The board in T 1607/08 recalled that the Guidelines published by the EPO were one of the sources of legitimate expectations. Therefore, where the Guidelines gave the clear indication that the continuation of the opposition proceedings had to be communicated to the patent proprietor, the latter was entitled to expect that such information would be given before a decision on the substantive issues was issued. Otherwise, as in the case at issue, the decision to revoke the contested patent would come as a surprise to the patent proprietor.

In T 182/90 (OJ 1994, 641), T 119/91, T 523/91, T 366/92 and T 397/94 the boards of appeal stated that it was not a substantial procedural violation within the meaning of R. 67 EPC 1973 if a request to be called back by or have an interview with the primary examiner was ignored. It was a matter for the examiner's discretion to decide whether to conduct such informal discussions in accordance with the Guidelines, bearing in mind the particular circumstances of the case (see also T 300/89, OJ 1991, 480).

The examining division's failure to follow a procedure set out in the Guidelines is not in itself a substantial procedural violation unless it also constitutes a violation of a rule or principle of procedure governed by an article of the Convention or one of the Implementing Regulations. This is because the Guidelines are not legally binding (T 42/84, OJ 1988, 251; T 51/94; J 24/96, OJ 2001, 434).

In T 246/08 the board saw, in the particular circumstances of the case, the examining division's deviation from the Guidelines as a matter for approval rather than reproach.

In T 313/10 the examining division had argued, using their own criteria, that a method performed by a computer was excluded. This was contrary to the established jurisprudence as set out in the Guidelines.

In T 1020/15 the board cited, in addition to applicable EPC provisions, numerous passages from the Guidelines (E‑IX, 1.2; C‑VIII, 1, C‑VIII, 3 and C‑VIII, 4; G‑IV, 7.5.3; E‑X, 7.1(i), E‑X, 7.3 and E‑X, 7.4) in support of its finding that the examining division's decision was vitiated by four substantial procedural violations.

According to the board in T 755/14, contrary to the appellant's view, although the search and examining divisions had failed to follow the procedure established in the Guidelines for considering unity, their substantively incorrect assessment of the unity issue could not be regarded as or equated to a substantial procedural violation within the meaning of R. 103(1) EPC, especially as the Guidelines were not legally binding. The board was also unable to identify any substantial procedural violation in the action then taken by the examining division.

In T 679/14, the board found, in line with the Guidelines (regarding postponements at the instigation of the Division, Guidelines, E‑II, 7.1), that it is unacceptable to repeatedly postpone oral proceedings without serious reasons, especially if it is done several times in the same examination proceedings after long delays have already occurred. In the case in hand, although the individual delays caused by the (eight) postponements were short, the examining division had acted against the interests of procedural efficiency, at the same time as ignoring clear rules given in the Guidelines to avoid such delays.