In Part 1, we explored the two main routes for entering Japan—Paris direct filing and the PCT national phase. In this Part 2, we turn to a practical question that arises once the route has been chosen: when the Japanese translation is due, and why translation quality matters for prosecution.

If your patent application starts in English, Japan offers more than one way to handle translation. A direct foreign-language filing lets you file the substantive application documents in a foreign language first and submit the Japanese translation later. A foreign-language PCT application follows a different timetable for entry into the Japanese national-phase.

The key deadlines to remember are 16 months for a direct foreign-language filing and 30 months for PCT national phase entry. But timing is only part of the story. The Japanese translation becomes the working text for ordinary amendments, so the quality of the translation can affect what you are able to claim later.

Why this matters

For a direct foreign-language filing, the Japanese translation is generally due within 16 months from the filing date or, if priority is claimed, from the earliest priority date. If that period is missed, the JPO issues a notice, and a further two-month period is available from the date of the notice. That mechanism is a safety net, not a timetable to plan around.

For a foreign-language PCT application, the standard deadline for Japanese national phase entry is 30 months from the priority date. If the national document for entry into the Japanese national phase is filed within the final two months of that period, a separate two-month period is available for filing the Japanese translation. Because this period is counted from the filing date of the national document rather than from the 30-month deadline itself, Japan should not be regarded as a straightforward 32-month country. For example, if the document is filed at 29 months, the translation is due at 31 months; only a filing on the last day of the 30-month period provides the full 32 months.

If a translation deadline is missed on either route and the application is deemed withdrawn, a request to restore rights may be available, but it requires an official fee and must be filed within strict time limits. Restoration is a genuine remedy, not a substitute for meeting the deadline, so contact Japanese counsel immediately rather than assuming the case is lost or that it can be easily revived.

Practical points

Translation quality matters because ordinary amendments are generally measured against the Japanese translation. During prosecution, translation errors can be corrected through a mistranslation-correction procedure that relies on the foreign-language original, in step with ordinary amendments. The real risk arises after grant: a post-grant correction of a mistranslation may not be allowed because correcting the error could be found to substantially enlarge or change the scope of the granted claims, even where the original text supports the correct meaning. An error that survives to grant may therefore become difficult or impossible to fix.

The foreign-language original still sets the outer boundary. A correction cannot add subject matter that was never disclosed in the original text. In practice, the safest approach is to treat claim terms, technical terminology, chemical names, units, and abbreviations as prosecution-critical language—not merely translation details.

What to prepare for Japanese counsel

• Final source-language application text and the intended Japanese filing route
• Priority information and the dates needed to calculate the 16-month or 30-month period
• Any PCT Article 19 or Article 34 amendments for a PCT case, plus instructions on how to use them
• A terminology list or preferred translations for key technical and claim terms
• Any known translation issued from a related filing

Takeaway

In Japan, translation is part of patent strategy, not just filing administration. Think 16 months for a direct foreign-language filing and 30 months as the basic PCT national-phase rule—and remember that a mistranslation left uncorrected at grant may not be fixable later.

Official basis checked: Patent Act Arts. 36-2, 184-4, 17-2 and 184-12; JPO Examination Guidelines on foreign-language written applications and international patent applications (current as of September 2026).

Disclaimer: This article is for general informational purposes only and does not constitute legal advice. Rules and practice may change, and outcomes depend on individual circumstances. For specific matters, please consult qualified patent counsel.