International Patents
Paris Convention Priority
12 months to file worldwide — without losing your original filing date as prior art shield.
Quick Answer
The Paris Convention gives inventors 12 months from their first patent filing to file in 179 member countries while keeping the original filing date as the priority date. That priority date blocks prior art published in the 12-month window — including the inventor's own disclosures — from being used against the foreign application.
The Timeline
How the 12-Month Window Works
Day 0
File priority application (U.S. provisional, U.S. nonprovisional, or first national filing)
Month 1–12
Priority window open. Publish, present, license, or raise funding freely — these events don't create prior art against foreign applications claiming your Day 0 priority.
Month 12
DEADLINE: File PCT application and/or direct national applications claiming priority. Missing this date = loss of priority; foreign filings treated as filed on actual date.
Month 18
PCT international publication (18 months from priority). Application publishes worldwide — prior art for everyone else.
Month 30
PCT national phase entry due (most countries). 31 months for some. Pay national fees; submit translations.
Requirements
Paris Convention Article 4 — Conditions for Priority
To validly claim Paris Convention priority, the subsequent filing must meet four conditions under Paris Convention Article 4:
Same applicant or successor in title
The priority application and the subsequent application must have the same applicant, or the applicant must have acquired rights from the original filer. Assignment of priority rights must be documented.
Same invention
The subsequent application must claim the same invention as the priority application. A subsequent claim covering subject matter not disclosed in the priority application does not benefit from the priority date for that subject matter — it gets the actual filing date.
Regular first application
The priority application must be a 'regular national filing' — meaning a regular filing in any Paris Union country that establishes the filing date. A PCT application can serve as the priority application for subsequent national filings.
Filed within 12 months
The subsequent application must be filed within 12 months of the FIRST filing of any application for the same invention in any member country. If you file in the U.S. in January, then file in Canada in March (a new first filing), you get 12 months from January — not from March.
PCT Strategy
Paris Convention Priority + PCT = Global Filing Strategy
Most applicants use the Paris Convention priority window in combination with the Patent Cooperation Treaty (PCT) for an efficient global filing strategy:
File U.S. provisional
File a U.S. provisional application (35 U.S.C. § 111(b)) — inexpensive, no claims required, establishes priority date. This starts the 12-month clock.
File PCT at 12 months
Before the 12-month deadline, file a PCT application claiming priority from the provisional. PCT designates 153+ countries in one filing. National phase entry due 30 months from priority.
Direct national filings
For countries not in PCT (Myanmar, Taiwan, Venezuela, Ecuador) or where direct filing is strategically preferred, file direct national applications claiming Paris Convention priority before month 12.
National phase at 30 months
Enter national phase in chosen countries (U.S., EU via EPO, China, Japan, Korea, India, etc.). Pay national fees, submit translations. The priority date from day 0 controls prior art for all.
FAQ
What is the Paris Convention priority period?
Under Article 4 of the Paris Convention for the Protection of Industrial Property (1883, revised through 1967), a person who files a regular national patent application in any Paris Union member country gains a 12-month priority right: they may file applications in any other member country claiming the original filing date as the priority date, provided the subsequent applications are filed within 12 months of the first filing. As of 2024, 179 countries are Paris Union members.
Why does priority date matter for foreign patent applications?
The priority date determines the prior art cutoff date. Any prior art published or filed between the original filing date and the subsequent foreign filing date is NOT counted as prior art against the subsequent application — the subsequent application is treated as if it had been filed on the original priority date. This is critical because the inventor's own disclosures, third-party publications, and competing patent applications published in that 12-month period cannot be used to reject the foreign application.
How do you claim Paris Convention priority in a foreign application?
When filing the foreign application, you must: (1) file within 12 months of the priority application's filing date; (2) include a priority claim identifying the original application by application number, filing date, and country; (3) provide a certified copy of the priority application (required by most national offices); (4) provide a translation if required. If filing via PCT, the priority claim is made in the PCT request form (Box VI) and carries forward to all designated national phases.
What happens if you miss the 12-month Paris Convention deadline?
Missing the 12-month deadline means your foreign applications lose the benefit of the priority date — they are treated as if filed on the actual foreign filing date. Any prior art published between the original filing and the missed foreign filing becomes relevant and can be cited against your application. Some countries (including EPO under EPC Rule 135) permit restoration of priority rights if the delay was unintentional, upon petition filed within 2 months of the missed deadline.
How does Paris Convention priority interact with PCT applications?
PCT applications are one of the most common vehicles for exercising Paris Convention priority. You file a national or provisional application, then file a PCT application within 12 months claiming priority. The PCT application can designate all PCT member countries (153 as of 2024) simultaneously, with national phase entry typically due 30 months from the priority date (31 months for some countries). This gives the applicant 18 additional months (30 - 12) after PCT filing before national phase fees are due.
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