How to Calculate PCT National Phase Deadlines

The Starting Point: The Priority Date

Every PCT national phase deadline is measured from the priority date, defined in PCT Article 2 as the filing date of the earliest application whose priority is claimed. If the PCT application claims no priority, the international filing date is the priority date.

This matters because a PCT application is usually filed near the end of the twelve-month Paris Convention priority period. A team that counts thirty months from the international filing date will calculate a deadline almost a year too late.

Step 1: Identify the Earliest Priority Claim

Check the PCT request form and the international publication front page for every priority claim. Where the application claims several earlier filings, such as two US provisional applications, the earliest one controls.

If a priority claim is withdrawn before the relevant deadline expires, the time limits are recalculated from the new earliest priority date. Applicants sometimes withdraw a claim deliberately to gain time, but doing so also moves the eighteen-month publication date and can expose the application to intervening prior art. That decision needs attorney review.

Step 2: Apply Each Office's Time Limit

PCT Article 22 sets the baseline at thirty months from the priority date. Many offices allow more. As general reference points:

• Thirty months: United States, Japan, China, Canada, and many others
• Thirty-one months: European Patent Office, Korea, India, Australia, and a number of others

Some offices also provide relief after the regular deadline. China accepts entry up to thirty-two months with a surcharge. Canada permits late entry within a further twelve months on request and payment of a fee, subject to conditions. Other offices have their own rules, and a few still apply a twenty-month limit in certain circumstances.

Time limits and late-entry provisions change. The authoritative source is the national phase chapter of the WIPO PCT Applicant's Guide and WIPO's table of time limits for entering the national phase, which should be checked for every office in the filing plan.

Step 3: Calculate the Calendar Date

Add the months to the priority date. If the priority date is 10 March 2025, the thirty-month date is 10 September 2027 and the thirty-one-month date is 10 October 2027.

When a deadline falls on a day the relevant office is closed, PCT Rule 80.5 and national law generally extend it to the next business day. Treat that extension as a safety margin, not as the working deadline.

Step 4: Confirm What Entry Requires in Each Office

National phase entry is more than a fee payment. Requirements typically include:

1. Translation of the application into the office's language, often including amended claims
2. National fees, and in some offices examination fees at entry or later
3. Appointment of a local agent where the office requires one
4. Supporting documents such as a power of attorney or priority document, some of which may be filed later

In the United States, entry under 35 U.S.C. § 371 requires the basic national fee and, if not already communicated by WIPO, a copy of the international application; the inventor declaration and an English translation can follow within set periods and surcharges. Filing a US continuation of the PCT application under 35 U.S.C. § 111(a) is an alternative route with different consequences, and the choice should be made deliberately.

Step 5: Docket Both the Legal and Working Dates

Good practice for docketing PCT national phase entry includes:

• Recording every national phase date for every office in the filing plan, not a single thirty-month reminder
• Setting internal instruction deadlines several months earlier, because foreign agents need time for translations
• Recording the Chapter II demand deadline, generally twenty-two months from priority or three months from transmission of the international search report, whichever is later
• Re-checking all dates whenever a priority claim is added, corrected, or withdrawn

Common Errors

The mistakes that cause lost rights tend to repeat:

• Counting from the international filing date instead of the priority date
• Assuming every office allows thirty-one months because the EPO does
• Relying on late-entry provisions that require a showing the applicant cannot make
• Instructing foreign agents so late that translations cannot be completed in time

Keeping National Phase Decisions on Schedule

National phase entry is often the single largest spending decision in a patent family's life, and it arrives at a fixed date whether or not the business has decided which countries matter. Teams that review each family several months before the thirty-month date, with its search results and commercial relevance in hand, make better choices than teams that decide under deadline pressure. ArcPrime's global filing strategy tooling tracks each family's national phase dates by office alongside the cost of each country list.