The aim of the EPO as ISA is to issue international search reports which are as complete as possible. Nevertheless, there are situations in which the search report and the written opinion cover only part of the subject-matter claimed, or in which no search report is issued. This may be either because the international application includes subject-matter which the ISA is not required to deal with (see GL/PCT‑EPO B‑VIII, 2) or else because the description, claims or drawings fail to meet a requirement, such as clarity or support of the claims by the description, to such an extent that no meaningful search can be made of all or some of the claims (see GL/PCT‑EPO B‑VIII, 3). Applications of the latter kind are often referred to as "complex applications".[GL/ISPE 9.01; ]

The same approach is taken as for European applications.

In principle, a declaration of no search under Art. 17(2)(a)(ii) should remain an exception. Under the PCT, even if the applicant amends the claims to overcome the objection, an additional search is not possible. When a declaration of no search is issued, the search must be performed at the examination stage without requesting an additional fee if the international application enters the European phase before the EPO and if the objection leading to the declaration has been overcome (GL/EPO C‑IV, 7.2). Therefore, at least some effort should be made to carry out a meaningful search of at least part of the claimed subject-matter.[Art. 17(2)(a)(ii); GL/ISPE 9.40; ]