PA 09/2016: Differences between international search and supplementary international search

WARNING: Although the information which follows was correct at the time of original publication in the PCT Newsletter, some information may no longer be applicable; for example, amendments may have been made to the PCT Regulations and Administrative Instructions, as well as to PCT Forms, since the PCT Newsletter concerned was published; changes to certain fees and references to certain publications may no longer be valid. Wherever there is a reference to a PCT Rule, please check carefully whether the Rule in force at the date of publication of the advice has since been amended.

Q:  I would like to minimize the likelihood of new prior art being cited in the national phase, and have seen that it is possible to request a supplementary international search on an international application.  Please could you explain to me what the differences are between an international search and a supplementary international search?

A:  International search is automatically carried out on all international applications (except in the case where the International Searching Authority (ISA) declares that no international search report (ISR) will be established under PCT Article 17.2).  Supplementary international search is an optional search which can be requested in addition to the international search. 

The main international search covers the PCT minimum documentation as well as additional documentation which would be searched by the ISA in its role as a national (or regional) Office.  Some Authorities specified for supplementary search (SISAs) offer a full search, covering their entire documentation as they would do if they were conducting the main international search, but some may offer different scopes of search, and may therefore charge different levels of supplementary search fees.  For example, they might offer a limited search covering documents in a particular language or languages, or in a particular technical field, in addition to offering a full search.  Requesting a supplementary international search could therefore expand both the linguistic and the technical scope of the search, which should further reduce the risk of new prior art being cited in the national phase.

Some of the other differences between the two types of search are described below.

How to request a search; language of search request

The applicant does not need to specifically request that an international search be carried out – the filing of the international application, in effect, constitutes a request to perform an international search.  Supplementary international search is optional and must be specifically requested.  This should preferably be done by completing Form PCT/IB/375 (Supplementary Search Request), which is available in editable PDF format on the PCT website at:  The form can then be uploaded in ePCT via the Upload Documents feature. 

Only one international search will be carried out by the ISA.  However, in the case of supplementary international search, if the applicant wishes to have separate supplementary international searches carried out by more than one SISA and is willing to pay the extra fees that this will entail, it is possible to request more than one supplementary international search on the same international application.  A separate supplementary search request form would need to be submitted for each SISA.

Note that the supplementary search request should be submitted to the International Bureau (IB) in either English or French.

Choice of searching authorities

In the case of an international search, the Offices which are available for the applicant to choose as ISA are essentially decided by the receiving Office with which the international application in question is filed and, in most cases, it is a fairly short list (and in some cases there is only one competent ISA).  When requesting supplementary international search, however, the applicant is free to choose any ISA which has notified the IB that it is prepared to carry out supplementary international searches, provided that it is not the ISA which is carrying out/has carried out the main international search (PCT Rule 45bis.9(b)).  Following the recent addition of three more Offices (the Intellectual Property Office of Singapore, the State Intellectual Property Service of Ukraine and the Visegrad Patent Institute), there are currently nine Offices which act as SISAs (out of the 21 active ISAs), as follows:

AT    Austrian Patent Office

EP    European Patent Office

FI      Finnish Patent and Registration Office

RU   Russian Federal Service for Intellectual Property, Patents and Trademarks

SE    Swedish Patent and Registration Office

SG    Intellectual Property Office of Singapore

UA    State Intellectual Property Service of Ukraine

XN    Nordic Patent Institute

XV    Visegrad Patent Institute

Please note that certain SISAs may have specified limitations and conditions as to the subject matter for which supplementary international searches will be carried out beyond those limitations that have been made in respect of the main international search and, in addition, limitations as to the total number of supplementary international searches which will be carried out in a given period.  For information on any limitations as to the scope of the supplementary international search, please see the PCT Applicant’s Guide, Annex SISA, for the respective Offices.

Time limit for requesting a search

The request for international search is effectively made at the time of filing the international application.  However, the applicant has until the expiration of 19 months from the priority date to submit the request for supplementary international search1, and so has time to carefully consider whether requesting supplementary international search would be the appropriate course of action for the application concerned.  Due to the fact that being in possession of the results of the main international search may help the applicant to determine whether a supplementary international search would be useful, in many cases, where time permits, requests for supplementary international search are submitted only once the applicant has received the ISR.

Fees payable for a search

Each ISA and SISA sets its own fees.  In some cases the fee payable for a supplementary international search carried out by a particular Office is the same as that which is payable for an international search carried out by it – for example, this is the case for the European Patent Office, the Finnish Patent and Registration Office and the Swedish Patent and Registration Office in their capacities as ISAs and SISAs.  In the case of some Offices, however, different fees are payable.  For example, the supplementary search fee may be lower where the search is being carried out only in certain languages, since less documentation will need to be searched.  Note that the Russian Federal Service for Intellectual Property, Patents and Trademarks in its capacity as SISA offers a full search of the PCT minimum documentation at a higher rate than its usual search of documents from the Commonwealth of Independent States specifically in the case where a declaration has been made by the ISA that no international search would be established because the subject matter concerns methods for treatment of the human or animal body.

For details of the fees payable at each Office, please see PCT Fee Table I(b).  In the case of the supplementary international search, a supplementary search handling fee (currently set at CHF 200) is also payable for the services provided by the IB. 

The fee payable for the international search is collected by the receiving Office, whereas the fees payable for the supplementary international search are both collected by the IB. 

Unity of invention

In the case of the main international search, if the ISA considers that unity of invention is lacking, it can ask the applicant to pay additional fees for the searching of multiple inventions (PCT Rule 40.1).  However, in the case of the supplementary international search, this option does not exist – if the SISA finds that the international application does not comply with the requirement of unity of invention, it will not invite the applicant to pay additional fees, and will only search one invention, the first one mentioned in the claims (Rule 45bis.6(a)).  The applicant can, however, when completing Box No. IV of the supplementary search request form, request the SISA to restrict the supplementary international search to one of the inventions which is not the main invention as identified by the ISA (as referred to in PCT Article 17(3)(a)) (see PCT Rule 45bis.1(d)). 

In the situation where the ISA has found that the international application does not comply with the requirement of unity of invention, and the ISR is available to the SISA before it starts the supplementary international search, it may exclude from the search any claims which were not the subject of the main international search (PCT Rule 45bis.5(d)).  The SISA is not obliged to agree with the ISA, however, and may make its own finding on unity of invention. 

Time limits for the establishment of search reports

The ISA should establish the ISR either three months from the date of receipt of the search copy by the ISA (usually within approximately 16 months from the priority date if priority is claimed) or nine months from the priority date, whichever time limit expires later (PCT Rule 42.1).  As far as the supplementary international search report (SISR) is concerned, the SISA will begin the supplementary international search upon receipt of the supplementary search request and only once the ISR has been established.  It will nevertheless start the search 22 months from the priority date, at the latest, if the ISR is late (PCT Rule 45bis.5(a)).  The SISR is to be established by 28 months from the priority date (PCT Rule 45bis.7(a)).

Contents of the search reports

The SISR is generally similar in contents and appearance to the main ISR.  It does not, however, contain comments on the title of the invention or the abstract, nor does it contain the classification of the subject matter.  Furthermore, it need not repeat relevant prior art documents which have already been cited in the ISR, unless this is necessary because of new relevance when read in conjunction with other documents discovered during the supplementary international search.  Sometimes, given that no written opinion is established with the SISR (unlike the main international search), the SISR may contain more detailed explanations concerning citations of documents than those which appear in the main ISR, since such additional details are helpful for a full understanding of the prior art.  Furthermore, it may contain additional comments on the scope of the supplementary search which has been conducted, which is of particular relevance when the supplementary search has been carried out without the benefit of the main ISR.

Publication of the search results

The ISR is published as part of the international application, promptly after the expiration of 18 months from the priority date (PCT Article 21.2(a)).  The SISR, however, will not be published per se, as part of the international publication.  Nevertheless, it will be made available to the public on PATENTSCOPE, as soon as it has been received by the IB, provided that the international application has already been published.  Both the ISR and any SISRs will be communicated to the designated Offices when the international application enters the national phase.

For further details on international search and supplementary international search, please see the PCT Applicant’s Guide, Introduction to the International Phase, Chapters 7 and 8, respectively;  for details about the ISAs and SISAs, please refer to the PCT Applicant’s Guide, Annexes D and SISA, respectively at:

For further information on supplementary international search, please also see the notes to the supplementary search request form and PCT Newsletters Nos. 12/2008, cover page, 04/2011, page 9 and 01/2012, page 10.

  1. The PCT Assembly, when it meets in October 2016, is going to consider extending that time limit to 22 months from the priority date.  If adopted, the consequential amendment to PCT Rule 45bis.1(a) would enter into force in July 2017 and would apply to international applications in respect of which the time limit for filing a request for supplementary international search under PCT Rule 45bis.1(a) as in force until 30 June 2017 had not yet expired on 1 July 2017.

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