According to the case law of the boards of appeal an examining division need not carry out an additional search if the technical features of the claims are notoriously well known. In particular, it is possible to raise an objection of lack of inventive step without documented prior art (see e.g. T 939/92, OJ 1996, 309; T 1242/04, OJ 2007, 421; T 1411/08). That should be allowable where the objection was based on "notorious knowledge" or indisputably forms part of the common general knowledge. In such cases it would be inappropriate to carry out an additional search for documented prior art on purely formal grounds (T 1242/04, OJ 2007, 421; see also T 690/06, T 698/11, T 779/11).

In T 359/11 the board held that where the relevant search authority has stated, either in a search report or in a declaration that no search report will be established, that it is not necessary to cite any documentary evidence of the prior art on the grounds that all of the technical features of the claimed invention are notorious, it is always incumbent upon the examining division to consider whether an additional search is necessary. The criterion to be applied is that if the invention as claimed contains at least one technical feature which is not notorious, the application should normally not be refused for lack of inventive step without performing an additional search (see T 690/06). In the case in hand, the choice of the examining division to decide on the issue of inventive step without performing an additional search could only be considered justifiable if the claimed subject-matter comprises no technical features which are non-notorious.

In T 2467/09 the examining division refused the application for lack of inventive step without making reference to documentary evidence. In fact, no prior art search was carried out in either the international phase or the European phase. The board noted that according to the established case law of the boards of appeal, an application should normally not be refused for lack of inventive step as long as no search has been performed. An exception may however be made in cases where the objection is based on knowledge that is "notorious" or indisputably forms part of the common general knowledge. The board pointed out that while it could not be reasonably disputed that server systems providing web pages were known at the priority date of the application, in the board's view this was less evident for "technologies for the dynamic building of web pages". While such technologies were probably well-known in 2008, which was when the examining division for the first time explicitly relied on their existence, it had to be kept in mind that the field of web technology had evolved considerably in the eight years following the filing of the priority application in April 2000. The board noted that the argument that certain knowledge is notorious is only a sufficiently cogent reason if it satisfies any reasonable addressee, i.e. if, at the time the argument is to be assessed by the applicant and, in case of an appeal, by a board of appeal, it cannot be reasonably disputed that that knowledge formed part of the common general knowledge of the skilled person at the effective filing date. In the case in hand, the board held that without documentary evidence, the examining division's reasoning failed to convince in this respect. The board remitted the case to the department of first instance for further prosecution. The examining division was to carry out an additional search on the basis of the claims, including the dependent claims. See also T 283/12.