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How to File a PCT International Patent Application: 30-Month Guide

April 26, 2026 Aruna 12 min read
filing a pct international patent application — intellectual property law and protection

For inventors and businesses seeking patent protection in multiple countries, the Patent Cooperation Treaty (PCT) provides a streamlined pathway to international patent protection. Filing a PCT international patent application is the most efficient and cost-effective way to preserve your international patent rights while deferring the significant costs of national phase filing. At PerspireIP, we have guided many clients through the PCT process, and this guide explains everything you need to know about how it works.

What Is the PCT System?

The Patent Cooperation Treaty is an international treaty administered by the World Intellectual Property Organization (WIPO) that provides a unified procedure for filing patent applications in its 157 member states. By filing a single PCT international patent application, you preserve the right to seek patent protection in any or all PCT member countries within 30 months (in most countries) from your earliest priority date. The PCT does not result in an international patent — patents are still granted by individual national or regional patent offices — but it provides an efficient gateway to multiple jurisdictions.

Key Stages of the PCT Process

The PCT international patent application process has two main phases: the international phase and the national phase.

The International Phase

The international phase begins when you file your PCT application and includes several important steps. First, an International Searching Authority (ISA) — such as the USPTO, the European Patent Office, or the Korean Intellectual Property Office — conducts an international search and issues a Written Opinion on patentability, typically within 16-18 months of your priority date. You then have the opportunity to file amendments to the claims and a response to the Written Opinion. Optionally, you can request International Preliminary Examination (Chapter II), which provides a more thorough examination and a second written opinion.

The National Phase

The national phase begins when you enter individual countries or regional patent offices to continue prosecution toward a granted patent. In most PCT member states, the national phase deadline is 30 months from your earliest priority date (some countries still have 20-month deadlines). At national phase entry, you pay national filing fees, provide translations where required, and appoint local patent agents to represent you before each national office.

Who Should File a PCT Application?

The PCT international patent application is the right choice for inventors and businesses that want patent protection in multiple countries but are not yet sure exactly which countries, or who want to defer the substantial costs of national phase filing while maintaining optionality. The PCT is particularly valuable for startups and growing companies that need 18-30 months to secure funding, assess market opportunities, and determine which countries are most commercially important before committing to expensive national filings.

Benefits of the PCT Pathway

Filing a PCT international patent application offers several significant advantages over filing directly in individual countries.

  • Cost deferral: filing a single PCT application costs significantly less than filing in multiple countries directly, and you defer the bulk of international filing costs by up to 30 months from your priority date.
  • Uniformity: a single application in a single language (for the international phase) covers all PCT member states simultaneously.
  • Prior art feedback: the international search report and written opinion provide valuable feedback on patentability before you commit to expensive national phase entry.
  • Prosecution leverage: a favorable written opinion can be used to accelerate examination in many national offices through the Patent Prosecution Highway.
  • Flexibility: you can enter only those national phases that make commercial sense based on market developments during the 30-month window.

PCT Filing Deadlines and Priority

A PCT application must be filed within 12 months of your earliest priority date (the filing date of your first patent application, whether provisional or non-provisional). If you file a US provisional application on January 1, 2025, you have until January 1, 2026 to file your PCT application. Missing this 12-month deadline means you lose the right to claim your original priority date in international filings — a critical error that can be fatal to international patent rights if prior art has appeared in the meantime.

Selecting the International Searching Authority

When filing a PCT international patent application, you must designate an International Searching Authority to conduct your prior art search. US applicants can typically choose the USPTO, the EPO, or certain other offices. The choice of ISA affects the cost of the international search, the thoroughness of the search, the likelihood of a favorable written opinion, and the databases searched. PerspireIP advises clients on ISA selection based on their technology area and strategic objectives.

National Phase Entry Strategy

At the 30-month deadline, you must decide which countries to enter. This is one of the most strategically important decisions in international patent prosecution. Key factors include your target markets, manufacturing locations, competitor locations, and the commercial value of the invention in each country. National phase entry in the European Patent Office covers 38+ European countries with a single application. Regional offices such as the African Regional Intellectual Property Organization (ARIPO) and the Eurasian Patent Organization (EAPO) provide similar regional coverage.

PCT Costs: What to Expect

PCT filing involves several layers of fees. The international filing fee (payable to WIPO) is approximately $1,800-$2,400 depending on the number of pages and whether reductions apply. The search fee (payable to the ISA) varies by office — the USPTO charges approximately $2,000 for large entities. Attorney fees for preparing and filing a PCT application typically add $3,000-$6,000. National phase entry costs then vary dramatically by country, from a few hundred dollars in some jurisdictions to several thousand in others, plus translation costs in non-English-speaking countries.

The PCT International Patent Application Timeline, Month by Month

Most PCT mistakes are calendar mistakes rather than drafting mistakes. Every deadline in the system runs from the priority date – not from the PCT filing date – so a single table of months is more useful than a description of stages.

  • 12 months – the PCT application must be filed within 12 months of the first national or regional application whose priority is claimed.
  • 16 months – one of the two possible cut-offs for amending the claims under Article 19 (see below).
  • 18 months – international publication occurs as soon as possible after the expiration of 18 months from the priority date. This is the moment the application becomes public, and it is not deferrable on request.
  • 22 months – the outer limit for requesting a supplementary international search under Rule 45bis.1(a), and one of the two possible cut-offs for a Chapter II demand.
  • 30 months – national phase entry under Articles 22 and 39 for most Contracting States.
  • 31 months – entry into the European regional phase at the EPO under Rule 159(1) EPC.

Two of those entries are later-of deadlines rather than fixed dates, which is where diary errors creep in. The Article 19 and Chapter II limits each depend on when the international search report was actually transmitted, so they cannot be calculated at filing – they have to be set when the search report arrives.

The practical consequence is that a PCT international patent application needs two docket passes: one at filing for the fixed dates, and one on receipt of the search report for the amendment and examination windows.

Article 19 and Article 34: Two Different Chances to Amend

Applicants routinely conflate these. They are separate rights, exercised at different times, before different bodies, and with different scope.

Article 19 lets you amend the claims only, once, and the amendment is filed with the International Bureau. Rule 46.1 sets the time limit as two months from the date of transmittal of the international search report to the International Bureau and to the applicant by the International Searching Authority, or 16 months from the priority date, whichever time limit expires later. In practice a late amendment may still be accepted if it reaches the Bureau before the technical preparations for international publication are complete, but that is a concession, not a deadline you should plan around.

The reason to use Article 19 is visibility. Amended claims are published with the application at 18 months, so third parties – and later, designated offices – see the claim set you actually intend to pursue rather than the one the search report attacked.

Article 34 is broader. During international preliminary examination you may amend the description, the claims and the drawings, and you amend before the International Preliminary Examining Authority rather than the Bureau. That is the route to take when the written opinion raises an objection that cannot be answered by narrowing the claims alone.

Neither amendment may add matter beyond the disclosure of the application as filed, and neither binds a designated office: every national or regional examiner is entitled to start again. What the amendments buy is a better written opinion going into the national phase, which is a negotiating position rather than a decision.

Two optional steps sit between the search report and the national phase. Both cost money and neither is automatic, so the question is when they change an outcome.

International preliminary examination (Chapter II). Under Rule 54bis.1(a) the demand must be made within three months from the date of transmittal to the applicant of the international search report or the declaration referred to in Article 17(2)(a), and of the written opinion established under Rule 43bis.1, or 22 months from the priority date, whichever expires later. The output is an international preliminary report on patentability. It is not binding, but a favourable one is genuinely useful where you intend to use an accelerated examination route, or where a licensee or investor is pricing the portfolio before the national phase resolves.

Supplementary international search. Rule 45bis.1(a) allows a request at any time prior to the expiration of 22 months from the priority date, carried out by an Authority other than the one that did the main search. The case for it is linguistic coverage: the main ISA may have searched thoroughly in English and German and barely touched Japanese, Korean, Chinese or Russian collections. If your field has heavy non-Latin-script prior art, a supplementary search surfaces it at 22 months instead of at a national examiner’s desk three years later.

Where neither applies, the honest answer is to skip both and spend the money on the national phase. A PCT international patent application does not become stronger for having more optional reports attached to it.

Where the 30-Month Rule Is Not 30 Months

The headline figure is 30 months, and for most designated offices that is correct. But the national phase deadline is set office by office, and treating 30 months as universal is one of the few PCT errors that is not recoverable.

The most important variation for European filers is the EPO, where Rule 159(1) EPC sets the time limit for the acts required to enter the European phase at 31 months from the filing date or, where priority is claimed, from the priority date. The EPO will not normally begin processing before that limit expires unless you file an express request for early processing.

Several other points are worth diarising alongside it:

  • Entry can always be made early. If you want a grant sooner, you do not have to wait for the 30- or 31-month date.
  • Translation requirements bite at entry, not at filing, and a translation of a long specification into several languages is usually the largest single cost in the whole process.
  • Missing an entry deadline may be remediable in some offices, but the remedies differ by jurisdiction and none of them is cheap or certain – they are not a plan.
  • A designated office is not bound by the international search report or the preliminary report; it examines afresh under its own law.

Because the cost of the national phase dwarfs the cost of the international phase, the decision that matters is which countries to enter. That is a commercial decision informed by a search, not a procedural one, and it should be made several months before the deadline rather than in the week before it.

Formalities That Get a PCT Filing Objected To

Before any of this, check whether you are cleared to file abroad at all: an invention made in the United States needs a foreign filing license under 35 U.S.C. 184 before it leaves the country. A PCT application can be substantively excellent and still draw an invitation to correct. The receiving Office and the International Bureau check form before anyone reads the invention, and three formalities account for most of what they send back.

The drawings. Rule 11.13(a) requires drawings executed in durable, black, sufficiently dense and dark, uniformly thick and well-defined lines and strokes without colorings, and Rule 11.5 caps the usable surface of a drawing sheet at 26.2 cm by 17.0 cm with minimum margins of 2.5 cm top, 2.5 cm left, 1.5 cm right and 1.0 cm bottom. Reference characters must be at least 0.32 cm high. Note that colour is not available here even though the EPO began accepting colour and greyscale drawings filed electronically on 1 October 2025 – a figure set that is now fine for a direct European filing is still irregular under the PCT. Our guide to PCT drawing requirements covers the whole rule.

The abstract. Rule 8.1(b) asks for an abstract as concise as the disclosure permits, preferably 50 to 150 words if it is in English or when translated into English. Abstracts drafted for a national filing are frequently well over that, and the Bureau will rewrite one it considers inadequate – which means losing control of the text that appears on the front page of the publication.

Sequence listings. Since 1 July 2022 any disclosure of nucleotide or amino acid sequences in an international application must comply with WIPO Standard ST.26, in XML, and this applies even where the priority application carried an older ST.25 listing. There was no transition period. For life-sciences filings out of a university or a young biotech this is the single most common formal defect we see.

None of these affects patentability. All of them cost time at exactly the point in the calendar where there is least of it.

How PerspireIP Supports PCT Applications

PerspireIP provides end-to-end PCT international patent application services, from preparation and filing of the international application through national phase entry in countries around the world. We maintain a network of trusted local patent agents in key jurisdictions globally, allowing us to coordinate seamless national phase entry on your behalf. We also provide strategic advice on which countries to enter, when to enter national phases, and how to use PCT prosecution feedback to strengthen your claims.

Conclusion

The PCT international patent application system is an essential tool for any inventor or company seeking meaningful international patent protection. It provides a cost-effective, flexible pathway to patent rights in 157 countries while deferring major costs and preserving strategic optionality. PerspireIP has the experience and global network to guide you through every stage of the PCT process. Contact us today to discuss your international patent strategy.