What is the Patent Cooperation Treaty (PCT)?
The Patent Cooperation Treaty (PCT) is an international treaty administered by the World Intellectual Property Organization (WIPO) that allows applicants to seek patent protection for an invention simultaneously in multiple countries by filing a single international application. The PCT currently has 158 Contracting States, meaning a single international filing can set the stage for patent protection across most of the world.
The PCT was adopted in Washington on June 19, 1970. It entered into force on January 24, 1978, when the first Contracting States became bound by it.
One point to understand at the outset: the PCT does not grant patents. The granting of patents remains under the control of the national or regional patent offices in each country where protection is sought. What the PCT provides is a centralized filing and early examination pathway that defers the most significant national costs and decisions until after applicants have had an opportunity to evaluate their invention's commercial and legal prospects.
Who can use the PCT
Any national or resident of a PCT Contracting State may file an international patent application under the PCT. PCT users span the full range of applicant types: major corporations, research institutions, universities, small and medium enterprises, and individual inventors.
The PCT versus the direct Paris Convention route
Applicants seeking multi-country patent protection have two main paths.
The direct Paris Convention route involves filing separate national or regional applications in each desired country within the priority period from the first filing date. That approach commits applicants early to identifying every target country, paying national fees in each jurisdiction, and engaging local counsel.
The PCT route uses a single international application that has the legal effect of a national patent application in all PCT Contracting States. This defers the moment when applicants must commit to individual countries, arrange translations, and retain local agents. The PCT is especially useful when the target country list is long or uncertain, or when applicants want to see the results of an international prior art search before committing national-phase spend.
| Factor | Paris Convention (direct) | PCT |
|---|---|---|
| Number of filings | Separate in each country | One international application |
| Early cost commitment | High (fees due in each country early) | Lower upfront; national costs deferred |
| Prior art search | Each office searches independently | Single ISA search during international phase |
| Decision timing | Target countries identified early | National phase entry can be deferred |
| Best when | Few target countries; speed priority | Many countries; large market uncertainty |
The international phase
After filing, the PCT application moves through an international phase managed by WIPO and the International Searching Authority chosen by the applicant.
Filing
Applicants typically file with their national patent office or directly with WIPO's International Bureau; regional patent office filing is also available to nationals of ARIPO, OAPI, Eurasian Patent Convention, or European Patent Convention member states. The application is submitted with one office, in one language, with one set of fees.
International search and written opinion
An International Searching Authority (ISA) conducts a high-quality search of relevant patent documents and technical literature in the major patent-filing languages and issues a written opinion on whether the invention appears to meet the patentability criteria. The written opinion is a preliminary and non-binding assessment: it reflects the ISA's view of whether the claims appear to satisfy novelty and inventive step in light of the search results, but no national office is bound by that assessment.
The search report and written opinion give applicants early intelligence on claim strength before committing to expensive national prosecution. Applicants may use that information to amend claims, narrow scope, or withdraw the application entirely if the search reveals a fatal prior art problem.
Optional supplementary search
Applicants may request one or more supplementary international searches by ISAs other than the primary ISA, extending prior art coverage into additional languages or technical fields. This reduces the risk of damaging prior art surfacing for the first time at national examination, when the cost of responding to it is much higher.
International publication
WIPO publishes the international application and the international search report on PATENTSCOPE after the expiration of the prescribed period from the priority date. Until that publication, the file is confidential: no third party may access the application unless the applicant explicitly authorizes it. Publication places the application in the searchable public record and notifies third parties of the pending international filing.
Optional international preliminary examination
International preliminary examination is an optional second evaluation. Applicants may submit amendments to the claims and description, argue against the written opinion's conclusions, and in many cases hold an interview with the examiner. The output is an International Preliminary Report on Patentability (IPRP) Chapter II, providing a refined assessment of patentability on the (potentially amended) application.
The IPRP is shared with national offices at the start of the national phase but is non-binding on their grant decisions. National offices conduct their own examination under their own laws and may reach different conclusions. A favorable IPRP can streamline national prosecution and accelerate examination in offices that give it significant weight; an unfavorable IPRP signals where claims remain vulnerable before national fees are committed.
The national phase
After the international phase, applicants must enter the national phase by filing separately with each national or regional office where they seek protection. National phase entry requires paying the relevant national fees, submitting translations where the target office requires them, and appointing local patent counsel. Each national or regional office then examines the application under its own law and decides independently whether to grant a patent.
WIPO administers the PCT system throughout: it receives and stores applications, performs formality examinations, publishes applications on PATENTSCOPE, and communicates documents to the relevant national offices.
Practical notes for practitioners
- The PCT is a filing and search system, not a patent grant. Clients frequently conflate "PCT application filed" with "patent obtained." Set expectations early: a PCT filing keeps options open across many countries simultaneously; it does not deliver a patent in any of them.
- Match the route to the target country set. If realistic protection is sought in only one or two foreign jurisdictions, the direct Paris Convention route avoids PCT system overhead and may be faster. The PCT makes sense when the target country list is long, uncertain, or likely to expand.
- Treat the written opinion as early intelligence, not a verdict. A negative written opinion does not foreclose national examination, but it identifies where claims are vulnerable. Use it to amend early or to counsel the client on realistic prosecution prospects before national-phase spend is committed.
- Supplementary searches reduce national-phase surprises. If the primary ISA covers only limited languages and the technical field has significant non-English prior art, supplementary searches in the relevant language coverage reduce the risk of adverse findings appearing first at national examination.
- Verify national phase requirements jurisdiction by jurisdiction. Each office has its own deadlines, fee structures, translation requirements, and local agent rules. Consult the PCT Applicant's Guide national chapters and local counsel for each target jurisdiction before relying on general rules.