For every international application the EPO as ISA issues either an International Search Report (ISR) or, in exceptional cases, a "Declaration of Non-Establishment of International Search Report" (see point 255), and a Written Opinion of the International Searching Authority (WO-ISA).

The WO-ISA provides the applicant with a preliminary non-binding written opinion on the question whether the claimed invention appears to be novel, to involve an inventive step and to be industrially applicable. A WO-ISA established by the EPO as ISA will be comparable to the written opinion established by the EPO for a Euro-direct application (ESOP) (see point 220).

The ISR is established within three months from receipt of the search copy at the EPO as ISA or within nine months from the earliest priority date, whichever time limit expires later. 

As from 1 January 2018, an information sheet ("Information on Search Strategy") is annexed to all search reports drawn up by the EPO under both the PCT and EP procedures. This information sheet contains details about the databases and keywords used by examiners to retrieve the relevant prior art, as well as the classification symbols defining the extent of the search. Information sheets are made available via file inspection on WIPO’s PATENTSCOPE and in the European Patent Register upon publication of the search report. 

If the EPO acted as ISA (but not as IPEA), the applicant must provide a substantive response to any deficiencies set out in the WO-ISA ("negative WO-ISA") upon entry into the European phase ("mandatory response") (see points 502 ff).