PCT International Search and Preliminary Examination Guidelines
2.20 International Searching Authorities may offer supplementary international searches as an optional additional service for applicants. Such searches are intended as a complement to the main international search, recognizing the fact that no search can be completely exhaustive. A supplementary search may be particularly relevant where the Authority conducting it has language specialization that is not available in the Authority conducting the main international search. The applicant can request a supplementary search from any Authority which offers the service (except the Authority conducting the main search) at any time before 22 months from the priority date. More than one supplementary search may be requested from different Authorities offering the service.
2.21 Many of the details of the service provided are decided by the Authority which is to carry out the supplementary search. The scope of the service is set out in an annex to the agreement between the International Bureau and the Authority, and details are published in Annex SISA of the PCT Applicant’s Guide. Features of the supplementary search procedure, including conditions, limitations and time limits, are discussed in more detail in paragraphs 15.76 to 15.97 and also in paragraphs 9.42 and 16.03.