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PCT Newsletter 01/2019: Practical Advice

WARNING: Although the information which follows was correct at the time of original publication in the PCT Newsletter, some information may no longer be applicable; for example, amendments may have been made to the PCT Regulations and Administrative Instructions, as well as to PCT Forms, since the PCT Newsletter concerned was published; changes to certain fees and references to certain publications may no longer be valid. Wherever there is a reference to a PCT Rule, please check carefully whether the Rule in force at the date of publication of the advice has since been amended.

The extent to which the priority claim will be checked in the international phase

Q:  I have claimed priority of an earlier national application in my international application, and would like to know the extent to which the validity of the priority claim is checked in the international phase? 

A:  In brief, even though in certain cases the International Searching Authority (ISA) and/or the International Preliminary Examining Authority (IPEA) may opine on the validity of the priority claim during the international phase, its validity is only definitively determined in the national phase by the designated Offices.  We will review some background on this topic.

The provisions that govern the right of priority are contained in Article 4 of the Paris Convention for the Protection of Industrial Property (“Paris Convention”).  It is recalled that any international application may contain a declaration referred to in PCT Article 8(1) (“priority claim”), claiming the priority of one or more earlier applications filed either in or for any country party to the Paris Convention or in or for any Member of the World Trade Organization that is not party to that Convention.  As far as PCT procedures are concerned, the priority claim is particularly important as it establishes a priority date for the purposes of computing time limits under the PCT (see PCT Article 2(xi)(a)). 

Although the receiving Office (RO) and the International Bureau (IB) do not consider the substantive validity of the priority claim, the RO will perform the first check, and the IB will perform a second check, that all the following information relating to the earlier claim is included in the priority claim, as required under PCT Rule 4.10:

  • the date on which the earlier application was filed (this will normally be considered as the priority date of the international application);
  • the serial number of the earlier application;
  • information as to where the earlier application was filed:
    • where the earlier application is a national application, the country party to the Paris Convention or the Member of the WTO that is not party to that Convention in which it was filed;
    • where the earlier application is a regional application, the regional Office with which it was filed1;
    • where the earlier application is an international application, the receiving Office with which it was filed.

If filing using ePCT‑Filing or PCT‑SAFE, the software will perform automatic validations, for example you will be notified of any missing or invalid element of the claim.  This should also be the case when using certain other electronic filing software, such as JPO PAS and EPO Online Filing. 

As well as checking that the date of filing of the earlier application is included, the RO and the IB will check that the international application has been filed within 12 months from the filing of the earlier application (that is, within the “priority period” (see PCT Rule 2.4)).  However, a priority claim will not be considered void only because the international filing date is later than the date on which the priority period expired, provided that it is within two months from that date.  This is to take into account the possibility of the applicant being granted restoration of rights in respect of the priority period either before the receiving Office in the international phase (PCT Rule 26bis.3) or before the designated (or elected) Offices in the national phase (PCT Rule 49ter.2). 

If there are any defects relating to the priority claim, for example, filing outside the period of two months from the expiration of the priority period of 12 months, any missing indications, or if the serial number or the date of filing of the earlier application do not match the number or date indicated on the priority document, the RO or IB will invite the applicant to submit a correction under PCT Rule 26bis.2.  Further information on the correction/addition of information relating to the priority claim will be published in a separate “Practical Advice” in the near future.

A priority claim would, where not corrected within the applicable time limit under PCT Rule 26bis.1(a), be considered not to have been made if:

  • the application, the priority of which is claimed, was not filed either in a country party to the Paris Convention or in a member of the WTO;
  • if the international application was filed more than two months after the expiration of the priority period; or
  • if the priority claim did not include the required details concerning the date on which and the country and/or Office, as the case may be, where the earlier application was filed.

As a result, the date of filing of the earlier application would not be used as a basis to calculate time limits under the PCT.

Please note, however, that according to PCT Rule 26bis.2(c), a priority claim will not be considered void only because:

  • the indication of the number of the earlier application referred to in Rule 4.10(a)(ii) is missing;
  • an indication in the priority claim is inconsistent with the corresponding indication appearing in the priority document; or
  • the international application has an international filing date that is later than the date on which the priority period expired, provided that the international filing date is within the period of two months from that date.

As far as ISA and, if applicable, the IPEA are concerned, generally, they will not make any investigation as to the validity of a right of priority.  However, in certain circumstances, for example, where the examiner has discovered a document that could constitute prior art but which was published on or after the priority date claimed and before the international filing date, he/she would then need to consider the validity of the priority date claimed. 

If the examiner has found the priority claim to be invalid, he/she will use the international filing date (or the earliest date of any other valid priority claims) as the relevant date for establishing the written opinion or international preliminary examination report, as the case may be, and reflect this in Box No. II of the opinion or report (see paragraph 6.06 of the International Search and Preliminary Examination Guidelines).  Note that the ISA or IPEA will not declare any priority claim void in itself and that the opinion or report of the ISA or the IPEA is not binding in the national phase.

Note that, in the national phase, the Designated Offices (DOs) may review any declaration made during the international phase that a priority claim is void for the purposes of the international phase.  DOs will check whether the applicant is the same applicant who filed the earlier application and, where this is not the case, or where the applicant’s name has changed, they may request documentation containing proof of the applicant’s entitlement to claim priority of the earlier application (PCT Rule 51bis.1(a)(iii)) (although this would not be necessary where a declaration under PCT Rule 4.17(iii) has been correctly made).  DOs may also check the validity of the priority claim in accordance with the Paris Convention during any substantive examination, such as whether the claimed subject matter was included in the earlier application.

For further information on requesting the restoration of the right of priority, please refer to the Practical Advice in PCT Newsletter No. 09/2015 at:


and the PCT Applicant’s Guide, International Phase, paragraphs 5.062 – 5.069 at:


  1. Where at least one of the countries party to the regional treaty concerned is neither party to the Paris Convention nor a Member of the WTO, the priority claim must indicate at least one country party to the Paris Convention or a Member of the WTO for which the earlier application was filed (PCT Rule 4.10(b)(ii)).