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Patent Cooperation Treaty

The Patent Cooperation Treaty (PCT) is an international patent law treaty that provides a unified procedure for filing patent applications to protect inventions in each of its contracting states. It was signed in 19 June 1970 and put into force in 24 January 1978. The contracting states constitute the International Patent Cooperation Union.

A patent application filed under the PCT is called an international application or PCT application. There is no international patent or PCT patent. Patents are only issued by national or regional patent offices.[1]: 45 Patent advocates, however, envision an international patent system based on PCT.[2]

The PCT route is one of the two ways that patents are granted in several countries with the same application. The other way is through the Paris route.[3]


To explain the nature of the PCT application,[4] Deputy Judge Peter Prescott put it as follows:[1]: 46

What, then, is an "international patent application"? It is a preliminary procedure conducted on the international plane which, should you choose to use it, will give you extra time before you need commit yourself to the expense of national patent applications and will reduce that expense if you do. This is how it works. A description of your invention in a single language is sent to an International Searching Authority. They search your invention against the prior art, and prepare a search report. The search report can help you decide whether it would be worth your while to go ahead and seek national protection – what is called "entering the national phase" – and if so, in how many countries, for each one of those will cost you money. (Think of the translation costs alone.) A still further advantage is that many national patent Offices will trust the international search report – although the Convention does not oblige them to do so – instead of searching the prior art themselves; and so you may be able to save quite a lot in search fees.

PCT applications also typically include broad claims,[1]: 48 though this is standard lawyer practice when filing patents anywhere.

When making a PCT application it is common to define the invention somewhat more broadly than you guess the national authorities will eventually allow, because it is good practice to start off wide and narrow down later in the light of the prior art that is cited against you – seeing that you cannot really know that prior art in advance. Even so, it is possible for the claim that is eventually granted to cover matter that does not fall within the claim of the PCT application.


Here is a more detailed description of the procedure for the PCT application.

International phase

Filing an international application

The first step of the procedure consists in filing a PCT application with a competent patent office, called a Receiving Office (RO).[5] The application can be in any language as long as it is accepted by the RO.[6] Any resident or national of a PCT contracting state can file an application.[7] Upon filing of the PCT application, all contracting states are Fy designated.[8] Subject to reservations made by any contracting state, a PCT application fulfilling the requirements of the treaty and accorded a PCT filing date has the effect of a regular national application in each designated state as of the PCT filing date.[9]

International search and written opinion

After filing the PCT application, three copies are created; one copy is kept by the RO ("home copy"), one copy is transmitted to the International Bureau of WIPO ("record copy"), and another copy ("search copy") is transmitted to the competent International Searching Authority (ISA).[10][note 1] An international search is then made by an ISA to find the most relevant prior art documents regarding the claimed subject matter.[11] The search results in an international search report (ISR), together with a written opinion regarding patentability.[note 2] The ISR is then transmitted to the applicant and the International Bureau but is not published.[12] Upon receiving the ISR, the applicant has the option to amend the claims of their PCT application by filing amendments with the International Bureau,[13] as well as request a supplementary international search.[14] Finally, the PCT application is also communicated to the designated patent offices.[15]

The ISA can choose not to conduct an ISR if it considers that the PCT application relates to a subject matter which the ISA is not required, under the Regulations, to search.[16] The said subject matter is defined by Rule 39 of the Regulations and mentions computer programs.

No International Searching Authority shall be required to search an international application if, and to the extent to which, its subject matter is any of the following:

(i) scientific and mathematical theories,
(ii) plant or animal varieties or essentially biological processes for the production of plants and animals, other than microbiological processes and the products of such processes,
(iii) schemes, rules or methods of doing business, performing purely mental acts or playing games,
(iv) methods for treatment of the human or animal body by surgery or therapy, as well as diagnostic methods,
(v) mere presentations of information,
(vi) computer programs to the extent that the International Searching Authority is not equipped to search prior art concerning such programs.

However, none of the above affects the issue of whether the invention is patentable under the laws of the contracting states:[17]

Nothing in this Treaty and the Regulations is intended to be construed as prescribing anything that would limit the freedom of each Contracting State to prescribe such substantive conditions of patentability as it desires. In particular, any provision in this Treaty and the Regulations concerning the definition of prior art is exclusively for the purposes of the international procedure and, consequently, any Contracting State is free to apply, when determining the patentability of an invention claimed in an international application, the criteria of its national law in respect of prior art and other conditions of patentability not constituting requirements as to the form and contents of applications.


The PCT application is published by the International Bureau at the WIPO in one of the ten "languages of publication": Arabic, Chinese, English, French, German, Japanese, Korean, Portuguese, Russian, and Spanish.[18] There are two formats: the full text of the application and the gazette. The publication normally takes place "promptly" after 18 months from the filing date or, if a priority is claimed, from the earliest priority date. However, the applicant may also ask an early publication.[19]

From the publication of the PCT application until 28 months after the priority date, any third party may file observations regarding the novelty and inventive step of the invention. The observations may be submitted anonymously, and no fee is due for filing such observations.[20]

The public can only view the PCT application once it's published.[21]

Preliminary examination

If the applicant chooses not to proceed further, the written opinion becomes final and is converted into an international preliminary report on patentability under Chapter I (IPRP Chapter I) of the PCT.[22][note 3] Else, the applicant can demand an international preliminary examination by an International Preliminary Examination Authority (IPEA). This results in the International Preliminary Examination Report (IPER), or the international preliminary report on patentability under Chapter II (IPRP Chapter II), as it is called since 2004.[23] The IPRP formulates a preliminary and non-binding opinion regarding patentability.[24] Applicants usually request a preliminary examination when there were negative findings of the written opinion of the ISR, and it is also an opportunity to amend their claims.[25] An alternative to the filing of a demand for international preliminary examination is to file informal comments in response to the written opinion established by the ISA. The informal comments are submitted to the International Bureau, where they are kept in the file of the PCT application and, in the case where no demand is filed, forwarded to the designated offices.

Consequently, each application is always accompanied in the national phase by an examination report, either an IPRP (Chapter I) or an IPRP (Chapter II). The IPRP cannot be the subject of appeal.[26]

National phase

As soon as the PCT application is published, the applicant may proceed with the procedure defined by the national and regional patent offices.[27] Provided that a national patent is granted, the PCT application allows the patent holder to backdate their rights to the date when the international patent application was published.[28]


  1. According to Article 16(1) PCT, an ISA can be either a national office or an intergovernmental organization.
  2. According to Article 15(5)(b) PCT, a contracting state's national office can subject any national application filed with it to an international search.
  3. The terms "Chapter I" and "Chapter II", which refer to the corresponding chapters of the Treaty, are used to mean, respectively, an application for which international preliminary examination has not been expressly requested by the applicant and an application for which international preliminary examination has been expressly requested by the applicant.


  1. 1.0 1.1 1.2 Oxonica Energy Ltd v Neuftec Ltd [2008] EWHC (Pat) 2127.
  2. Khoury Amir H., The End of the National Patent Office, IDEA — The Intellectual Property Law Review, Vol. 52, No. 2, 2012, pp. 227–9.
  3. PCT FAQS (Question #2)[archived],
  4. PCT FAQS (Question #28)[archived],
  5. Article 10 PCT.
  6. Rule 12.1(a) Regulations PCT.
  7. Article 9(1) PCT.
  8. Rule 4(9)(a)(i) Regulations PCT.
  9. Article 11(3) PCT.
  10. Article 12(1) PCT.
  11. Article 15(1)(2) and (4) PCT.
  12. Article 18(2) PCT.
  13. Article 19(1) PCT.
  14. Rule 45bis(1)(a) Regulations PCT.
  15. Article 20(1)(a) PCT.
  16. Article(2)(a)(i) PCT.
  17. Article 27(5) PCT.
  18. Rule 48(3)(a) Regulations PCT.
  19. Article 21(2) PCT.
  20. Third Party Observations[archived],
  21. PCT FAQS (Question #22)[archived],
  22. Rule 44bis(1)(a) Regulations PCT.
  23. Article 31(1) PCT.
  24. Article 33(1) PCT.
  25. Article 41 PCT.
  26. Erstling Jay & Boutillon Isabelle, The Patent Cooperation Treaty: At the Center of the International Patent System, William Mitchell Law Review, Vol. 32, No. 4, 2006, p. 1596.
  27. PCT FAQS (Question #26)[archived],
  28. Article 29(4) PCT.

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