Introduction The Patent Co-operation Treaty (PCT) was concluded in 1970, amended in 1979, and modified in 1984 and 2001. It is open to States party to the Paris Convention for the Protection of Industrial Property (1883). The Treaty makes it possible to seek patent protection for an invention simultaneously in each of a large number of countries by filing an “international” patent application. Such an application may be filed by anyone who is a national or resident of a Contracting State*. It may generally be filed with the national patent office of the Contracting State of which the applicant is a national or resident or, at the applicant’s option, with the International Bureau of WIPO in Geneva. The international application is then subjected to what is called an “international search.” That search is carried out by one of the major patent offices appointed by the PCT Assembly as an International Searching Authority (ISA). The search results in an “international search report”, a listing of the citations of such published documents that might affect the patentability of the invention claimed in the international application. At the same time, the ISA prepares a written opinion on patentability.
The international search report and the written opinion are communicated by the ISA to the applicant, who may decide to withdraw his application, in particular where the report or opinion makes the granting of patents unlikely.
If the international application is not withdrawn, it is, together with the international search report, published by the International Bureau. The written opinion is not published.
The procedure under the PCT has great advantages for the applicant, the patent offices and the general public:
(i) the applicant has up to 18 months more than he has in a procedure outside the PCT to reflect on the desirability of seeking protection in foreign countries, to appoint local patent agents in each foreign country, to prepare the necessary translations and to pay the national fees; he is assured that, if his international application is in the form prescribed by the PCT, it cannot be rejected on formal grounds by any designated Office during the national phase of the processing of the application; on the basis of the international search report or the written opinion, he can evaluate with reasonable probability the chances of his invention being patented; and the applicant has the possibility during the international preliminary examination to amend the international application to put it in order before processing by the designated Offices;
(ii) the search and examination work of patent offices can be considerably reduced or virtually eliminated thanks to the international search report, the written opinion and, where applicable, the international preliminary examination report that accompany the international application;
(iii) since each international application is published together with an international search report, third parties are in a better position to formulate a well-founded opinion about the patentability of the claimed invention.Procedure Please select the appropriate stage in the procedure – these follow the standard letter organisation:
4.3.1 – IPA Preliminaries
4.3.2 – IPB Application to Search
4.3.3 – IPR National Phase Reminders
* Check that the proposed applicant is a national or resident of a Contracting State, because there are problems with Guernsey and Jersey companies, for example. These problems can be overcome by naming a UK-based inventor as a joint applicant, for example, but care should be taken to establish the correct assignments in place to support this.
Back to 4. Patent Procedures
Last Updated on 13 August 2025 by Keith