PCT application (PCT)

1. Claim priority, if there is a first filingA PCT application may claim the priority of earlier applications filed in or for any Paris Convention country (PCT Article 8)². Under the Paris Convention the priority period for patents is twelve months from the first filing³. An applicant can also file a PCT application directly, without an earlier application¹.
2. International search and written opinionAn International Searching Authority lists relevant prior art in an international search report and gives a written opinion on whether the claimed invention appears novel, inventive and industrially applicable^1,5. The report is due within three months of the authority receiving the search copy or nine months from the priority date, whichever expires later (PCT Rule 42.1)⁴.
3. International publicationThe International Bureau publishes the application promptly after 18 months from the priority date, unless the applicant asks for earlier publication or the application is withdrawn first (PCT Article 21)⁶.
4. Optional international preliminary examinationOn request, an International Preliminary Examining Authority carries out a second patentability evaluation, usually on an amended version of the application¹.
5. National phase entryThe applicant must furnish a copy, any required translation and the national fee to each designated or elected office no later than 30 months from the priority date (PCT Articles 22 and 39)^7,8. Each office then examines the application under its own law¹.

Under the treaty's own definitions, references to a "patent" mean national patents, granted by a national authority, and regional patents, granted by an authority with the power to grant patents effective in more than one state (PCT Article 2)⁹.

Thirty months from the priority date is the treaty's default time limit, but any national law may fix a time limit that expires later (PCT Article 22(3) and Article 39(1)(b))^7,8. WIPO's note to Article 22 adds that, for an office that has notified the International Bureau of incompatibility with its national law, the earlier 20-month time limit continues to apply⁷. Electing that state in a demand for international preliminary examination before the 19th month from the priority date brings the 30-month limit of Article 39 into play⁸.

• European Patent Office: the acts required to enter the European phase must be performed within thirty-one months from the filing date or, if priority has been claimed, from the priority date (Rule 159(1) EPC)¹⁰.
• Early entry: an applicant does not have to wait for the 30 months to expire and can always request early entry into the national phase¹.

WIPO describes two ways to protect an invention in several countries. Because patents are territorial, both end with separate national or regional rights¹.