Introduction
The Patent Cooperation Treaty (PCT) provides a streamlined procedure for applicants who seek patent protection for an invention in multiple countries. Instead of filing separate patent applications in every desired country at the beginning of the process, an applicant can file one international patent application under the PCT.
The PCT is administered by the World Intellectual Property Organization (WIPO). As of 2026, the PCT has 159 Contracting States. Importantly, a PCT application does not itself result in an international patent. Ultimately, patents are granted or refused by the national or regional patent offices during the national phase.
For patent applicants, understanding the PCT is particularly important when an invention may have commercial value in several countries.
Question: (True or False) A patent will NOT give you the right to exclude others from making, using, selling, offering for sale, or importing within the United States, its territories if they are carried out in foreign countries.
Answer: True.
What Is the Patent Cooperation Treaty?
The Patent Cooperation Treaty is an international treaty that permits an applicant to file a single international patent application that can be used to seek patent protection in multiple PCT Contracting States.
The PCT provides a common international procedure for:
- filing an international patent application;
- conducting an international search;
- receiving a written opinion concerning patentability;
- publishing the international application; and
- preparing for national or regional patent prosecution.
The PCT therefore simplifies the early stages of seeking patent protection internationally.
Does a PCT Application Grant a Patent?
No.
This is one of the most important concepts for applicants to understand.
A PCT application is not an international patent. There is no single “PCT patent” that automatically provides enforceable patent rights throughout the world.
After the international phase, the applicant generally must enter the national or regional phase in the countries or regions where patent protection is desired. The relevant national or regional patent office then determines whether a patent should be granted.
For example, an applicant may file one PCT application and later pursue patent protection in the United States, Europe, Japan, Korea, Canada, or other jurisdictions.
The national patent offices remain responsible for deciding whether the invention satisfies their respective patentability requirements.
The PCT International Phase
The PCT procedure can generally be divided into two major stages:
- International phase
- National or regional phase
The international phase begins with filing the PCT application. It includes several procedures designed to provide the applicant with information about the invention’s potential patentability.
WIPO describes the PCT international procedure as including filing, international search, and international publication, with international preliminary examination being an optional additional procedure.
Question: What are the two major phases of a PCT application?
Answer: International phase and National or Regional phase.
Filing the International Application
The applicant files a PCT international application with a competent receiving Office or, where permitted, with the International Bureau of WIPO.
A PCT application generally contains:
- a request;
- a description;
- one or more claims;
- drawings, when required; and
- an abstract.
The claims are particularly important because they define the scope of protection being sought.
Question: (True or False) A PCT application need not contain one or more claims.
Answer: False.
The 12-Month Priority Period
A common reason for filing a PCT application is to preserve the benefit of an earlier national or regional filing.
If an applicant wants to claim priority to an earlier application for the same invention, the PCT application generally must be filed within 12 months of the earliest priority application.
Example
Suppose an applicant files a U.S. provisional patent application on January 10, 2026.
If the applicant wishes to claim priority to that application in a PCT application, the applicant generally should file the PCT application by January 10, 2027, subject to applicable rules concerning the calculation of the deadline and restoration of priority rights.
The priority claim can be important because it may establish an earlier relevant date for purposes of determining prior art and patentability.
International Search
After filing, an International Searching Authority (ISA) conducts an international search.
The purpose of the international search is to identify relevant prior art and provide information concerning the potential patentability of the claimed invention.
The applicant generally receives an International Search Report (ISR) together with a written opinion addressing certain patentability issues.
The international search can be valuable because it gives the applicant an early indication of how the claims compare with known prior art before national-phase prosecution begins.
Question: When is an International Search Report (ISR) due?.
Answer: About 16 months from the priority date.
International Publication
The international application is generally published approximately 18 months from the priority date.
Publication makes the application available to the public and provides information about the invention and the applicant’s international filing.
Applicants should therefore consider carefully what information is disclosed in the PCT application before filing.
Question: When is an international patent generally published?.
Answer: About 18 months from the priority date.
International Preliminary Examination
The applicant may also request international preliminary examination under the applicable PCT procedures.
This examination can provide additional information concerning the potential patentability of the invention.
However, an international preliminary examination does not determine whether a national patent will ultimately be granted. National and regional patent offices retain authority over examination and grant.
Question: (True or False) It is optional that an international preliminary examination is requested.
Answer: True.
Entering the National Phase
After the international phase, the applicant must decide where patent protection is actually desired.
For example, an applicant might decide to pursue protection in:
- the United States;
- European countries through the appropriate regional system;
- Japan;
- Korea;
- Canada; or
- other PCT Contracting States.
The applicant must satisfy the requirements of the relevant national or regional patent office.
For the United States, the PCT application enters the U.S. national stage under 35 U.S.C. § 371.
Section 371 establishes requirements for commencing the U.S. national stage, including payment of the applicable national fee and, when required, submission of an English translation and other documents.
Question: What are the requirements for commencing the U.S. national stage?
Answer: Payment of the applicable national fee, submission of an English translation, and submission of oath or declaration.
PCT Chapter I and Chapter II
The PCT procedure is commonly discussed in terms of Chapter I and Chapter II.
Chapter I
Chapter I generally involves:
- filing the international application;
- international search;
- preparation of the written opinion; and
- international publication.
The written opinion provides an assessment of issues concerning the patentability of the claimed invention.
Chapter II
Chapter II provides an optional international preliminary examination procedure.
An applicant may use this procedure to obtain a more detailed preliminary examination before proceeding to the national phase.
The results can help an applicant evaluate whether particular claims should be amended or whether it is worthwhile to continue pursuing protection in particular countries.
Question: What is a distinction between Chapter I and Chapter II in a PCT application?
Answer: In Chapter I, the International Searching Authority establishes the International Search Report (ISR) and the Written Opinion of the ISA (WO-ISA) and in Chapter II, the applicant generally files a Demand for International Preliminary Examination and establishes International Preliminary Report on Patentability (IPRP Chapter II).
PCT and Patent Prosecution Strategy
The PCT can be useful as a strategic tool in patent prosecution.
For example, an applicant may not know immediately which foreign markets will be commercially important. Filing a PCT application can provide additional time to evaluate:
- the commercial potential of the invention;
- the results of the international search;
- potential patentability problems;
- licensing opportunities;
- foreign filing costs; and
- which countries justify further prosecution.
This additional time can be especially useful because pursuing patents separately in many countries can be expensive.
PCT Does Not Replace National Patent Examination
Applicants should not assume that a favorable international search or written opinion guarantees a patent.
Each national or regional patent office applies its own applicable patent laws and examination procedures.
For example, when a PCT application enters the U.S. national stage, the USPTO examines the application under U.S. patent law.
Therefore, an applicant may receive a favorable international search result but subsequently encounter a rejection during U.S. prosecution.
Similarly, a claim that is considered allowable in one jurisdiction may encounter a different patentability issue in another jurisdiction.
Question: (True or False) A PCT replaces regular filings in the respective countries.
Answer: False.
Example of PCT Prosecution
Consider an inventor who develops a new medical device.
Step 1 — Initial Filing
The inventor first files a U.S. patent application.
Step 2 — PCT Filing
Within the applicable priority period, the inventor files a PCT application claiming priority to the earlier U.S. application.
Step 3 — International Search
An International Searching Authority searches the relevant prior art and issues an International Search Report and written opinion.
Step 4 — Evaluate the Results
The inventor and patent practitioner review the search results and determine whether the claims should be amended or narrowed.
Step 5 — Select Countries
The inventor evaluates commercial opportunities and determines which countries justify further patent prosecution.
Step 6 — National Phase
The applicant enters the national or regional phase in the selected jurisdictions.
Each patent office then conducts its own examination.
Advantages of the PCT System
The PCT system can provide several practical advantages.
One initial international filing
Instead of immediately preparing separate applications for numerous countries, the applicant can begin with one PCT application.
More time for decision-making
The international procedure generally gives the applicant additional time to determine where to pursue patent protection.
International search information
The international search provides potentially valuable information about relevant prior art.
Centralized early procedure
The PCT establishes common procedures for the initial international stage, reducing some of the administrative burden associated with multiple immediate foreign filings.
WIPO specifically identifies the PCT’s ability to save applicants time and effort when seeking protection in multiple countries as one of its principal advantages.
Disadvantages and Considerations
The PCT system also has limitations.
First, filing a PCT application does not eliminate the eventual cost of national patent prosecution.
When the applicant enters the national phase, additional fees may include:
- national filing fees;
- translation costs;
- attorney or patent agent fees;
- examination fees;
- maintenance or renewal fees; and
- other country-specific expenses.
Second, the applicant must carefully monitor PCT and national-phase deadlines.
Third, filing a PCT application does not guarantee patent protection.
PCT vs. Direct Foreign Filing
An applicant generally has two broad strategies for seeking foreign protection:
Direct national/regional filings: File applications separately in selected countries or regions.
PCT filing: File one international application and postpone the decision regarding specific national or regional filings until the national-phase stage.
The appropriate strategy depends on factors such as the invention, expected markets, available budget, priority dates, and commercial objectives.
Practical Checklist for Applicants
Before filing a PCT application, an applicant should consider:
- What is the earliest priority date?
- Has the 12-month priority deadline been calculated correctly?
- Which countries are likely to be commercially important?
- Has an appropriate patentability search been conducted?
- Are the claims supported by the specification?
- Are the drawings and description complete?
- Which receiving Office should be used?
- Which International Searching Authority is appropriate?
- What are the anticipated PCT fees?
- What countries might require national-phase entry?
- Have the applicable national-phase deadlines been calendared?
Conclusion
The Patent Cooperation Treaty provides an important international framework for seeking patent protection in multiple countries. It allows an applicant to begin the international patent process with a single application while obtaining an international search and additional time to evaluate foreign patenting strategies.
However, a PCT application should not be confused with an international patent. Patent rights are ultimately granted by individual national or regional patent offices during the national or regional phase.
For inventors and patent practitioners, understanding the relationship between the international phase and national-phase prosecution is essential for managing deadlines, costs, claim strategy, and international patent rights.
References
- World Intellectual Property Organization (WIPO), Introduction to the Patent Cooperation Treaty (PCT).
- WIPO, PCT Applicant’s Guide – International Phase. The Guide provides detailed information concerning the international and national phases of PCT procedure.
- WIPO, Filing a PCT Application. This resource explains filing requirements, priority claims, fees, and related procedures.
- USPTO, Patent Cooperation Treaty. The USPTO provides information concerning PCT international applications, Chapter I, Chapter II, and U.S. national-stage procedures.
- 35 U.S.C. § 371 – National Stage: Commencement. This statute establishes requirements for commencing the U.S. national stage of a PCT application.
- Patent Cooperation Treaty (PCT), WIPO. Information concerning the treaty, Contracting States, and PCT legal framework is available from WIPO.
Educational disclaimer: This article provides general educational information about U.S. patent prosecution. It is not legal advice and does not create an attorney-client relationship.