PCT Newsletter

September 2026 | No. 09/2026

Practical Advice

Filing a demand for international preliminary examination

Founded in 2011 as a spinoff from Kyoto University, FLOSFIA originally focused on water filtration but is now exploring the use of gallium oxide as an energy-saving alternative to silicon in power semiconductors. 

Q: We filed an international application under the PCT and recently received the written opinion of the International Searching Authority (ISA). Unfortunately, some of the results of the international search were unfavorable. Might it be worth filing a demand for international preliminary examination under PCT Chapter II? If so, what would this procedure involve?

A: In a nutshell, international preliminary examination is an optional procedure during the international phase which enables you to formally respond to the written opinion of the ISA and make amendments to your international application, instead of filing multiple responses in all the national Offices where you enter the national phase. You do this by filing a demand (Form PCT/IPEA/401) and paying the associated fees to a competent International Preliminary Examining Authority (IPEA). 

International preliminary examination is the only opportunity during the international phase for applicants to substantially interact with an examiner at an International Searching and Preliminary Examining Authority – albeit within a tight time frame. And it is also the only opportunity for an applicant during the international phase to amend the description and any drawings (PCT Article 34 and Rule 66), have any amendments examined, and submit arguments in response to any findings by the examiner. The applicant can also amend the claims during the international preliminary examination procedure and have them examined, unlike any claims submitted under PCT Article 19 before international publication during the international search procedure. 

The right to file a demand (PCT Rule 54)

At the time of filing the demand, there must be at least one applicant who is a resident or national of a PCT Contracting State. The right to file a demand may be lost if, after the intern1]ational filing date, the original applicant assigned the rights in the application to an applicant who is not a national or resident of a PCT Contracting State bound by Chapter II.[1]

Fees to pay after filing a demand (PCT Rules 57 and 58)

You will need to pay an international preliminary examination fee, the amount of which depends on which competent IPEA you have chosen, and a handling fee of CHF 200 for the International Bureau. Both fees are payable to the IPEA. For exact fee amounts, refer to the PCT Applicant’s Guide, Annex E. Fees are payable within one month from the date of the filing of the demand or 22 months from the priority date, whichever expires later. Pay the fees as soon as possible as examination will not start before they are paid (PCT Rule 69.1(a)).

Why might you choose to file a demand? 

As mentioned above, you need to file a demand if you wish to amend the description or drawings of your application. Filing a demand also provides the opportunity to submit formal comments for consideration by the examiner if you do not agree with an objection. It may give you a chance to improve your international application and get a fully positive international report in the international phase, which may be useful for commercial purposes. Whether the potential value to you of international preliminary examination outweighs the costs will depend on the number of Offices where you are interested in entering the national phase and any differences in substantive patent law. In some cases, it may be desirable to wait until the national phase and tailor the amendments and arguments to local laws and practices rather than filing a demand, for example to take into account differences among countries regarding patentable subject matter. 

When and where to file

While you may file a demand as late as close to the expiration of 22 months after the priority date, early start means more time for international preliminary examination. You should therefore review the international search results promptly when you receive them – typically around 16 months from the priority date – and decide as soon as possible whether to file a demand. When there is ample time, the examiner may be more inclined to provide you with additional opportunities for exchanges. 

Which IPEA you can use, and whether you can choose from among several possible IPEAs or have a single competent IPEA, will be determined by which Receiving Office you used. Some Authorities will, however, serve as an IPEA only when they conducted the international search. Before filing a demand, make sure the IPEA you are interested in is competent to examine your application; the relevant information can be found in the PCT Applicant’s Guide, Annexes C and E.

The procedure

Even if the IPEA concerned does not accept direct filings via ePCT, you can use ePCT to file a demand via the International Bureau (IB), which will direct the submission to the competent IPEA (PCT Rule 59.3). The demand will be considered to have been filed on the date the IB received it, while the one-month period for paying fees runs from the date of receipt by the IPEA.

In the demand form, you need to specify whether the IPEA should base the examination on 
the application as originally filed, amended under PCT Article 19, and/or amended under PCT Article 34, and attach any relevant amendments.

The IPEA will generally consider the written opinion of the ISA as its own first written opinion (PCT Rule 66.1bis(a)); it is not obliged to issue another written opinion in addition to the opinion issued by the ISA before it draws up the report that will conclude international preliminary examination. However, it must take into account any amendments or arguments received before it has started to draw up the report (PCT Rule 66.4bis). Practice regarding when an IPEA will issue a further written opinion or the report varies. You are therefore advised to check with the relevant IPEA directly; for some IPEAs, a further written opinion will be issued if you have filed a substantive response to the written opinion of the ISA and further objections need to be raised. However, if you do not know whether the IPEA is willing to issue a further written opinion, you should request an interview at the time of filing the demand to ensure at least one exchange with the examiner. 

The IPEA will also conduct a mandatory “top-up search” to discover relevant prior art documents that have been published or become available to the IPEA after the date on which the international search report was established (PCT Rule 66.1ter). Where such further prior art is used for objections, the applicant must be given the chance to comment. 

Note that the IPEA is only obliged to examine the claims searched by the ISA. If no search has been established with respect to all claims (PCT Article 17(2)(a), filing a demand will add no value. 

At the end of the examination, the IPEA will establish the international preliminary report on patentability, Chapter II (IPRP II), also referred to as the international preliminary examination report (IPER). While national Offices are not bound by the findings, a favorable report will usually facilitate national processing and allow accelerated processing before Offices participating in a Patent Prosecution Highway (PPH) agreement. 

Further information can be found in the Practical Advice in the following issues of the PCT Newsletter: 

  • 02/2026: Submitting amendments under PCT Article 34 after filing a demand for international preliminary examination
  • 09/2021: Requesting accelerated national phase processing of an international application 
  • 09/2020: Access by third parties to information in the file of the international preliminary examination
  • 06/2019: The timing of the start of the international preliminary examination (following the amendment to PCT Rule 69.1(a))
  • 04/2010 and 05/2010: Factors to be considered when deciding whether or not to file a demand for international preliminary examination (Parts I and II) 

Please also refer to the PCT Applicant’s Guide, Introduction to the International Phase, Chapter 10, for a detailed description of the Chapter II procedure. 

[1] Uruguay is not bound by the provisions of Chapter II, having made a declaration to that effect in accordance with PCT Article 64(1)(a).

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