Search and written opinion
A search or international search is then made by an authorized International Searching Authority (ISA) to find the most relevant prior art documents regarding the claimed subject matter. The search results in an International Search Report (ISR), together with a written opinion regarding patentability.
The ISR is normally provided by the ISA to the applicant 9 months after filing of the application in the event of a first filing and 16 months after the priority date in the event of a subsequent filing (i.e., claiming the priority of a first filing).
The ISR is published together with the international application (or as soon as possible afterwards). The written opinion is initially confidential, but unless it is superseded by an International Preliminary Examination Report (see optional examination, below), it is made available in the form of an International Preliminary Report on Patentability (Chapter I of the Patent Cooperation Treaty, or IPRP Chapter I), within 30 months of the filing date or a priority date, if any. If the ISR is not in English, it is translated into English for publication. A designated Office may require a translation of the IPRP Chapter I into English.
The international search report can help the applicant to decide whether it would be worthwhile to seek national protection, and if so, in how many countries, as it costs fees and other expenses, including costs of translation, to enter the national phase in each country. Yet another advantage of filing an international application under the PCT is that many national patent authorities will rely on the international search report (although the PCT does not oblige them to do so) instead of starting from scratch to search the prior art themselves, and the applicant may be able to save in search fees.
In addition to the compulsory international search, one or more optional supplementary international searches may also be carried out by participating International Searching Authorities, upon request by the applicant and payment of corresponding fees. The purpose is to reduce the likelihood of seeing new prior art being cited in the subsequent national phases. A supplementary international search is said to allow applicants to obtain an additional search report "taking into account the growing linguistic diversity of the prior art being found". In 2009 and 2010, the demand for supplementary international searches was relatively low.