Two questions were referred to the Enlarged Board of Appeal of the European Patent Office (hereinafter EPO) regarding priority.

The first question addressed the EPO’s authority to assess a party’s entitlement to priority.

The second question covers a special situation occurring where inventors filed a United States patent application, the priority from which was claimed in a subsequent international application under the Patent Cooperation Treaty (hereinafter PCT) with :

these inventors designated as applicants for the United States only ;
different applicants named for other States designated in the PCT application (including those under the EPO’s jurisdiction).

The question addressed whether a co-applicant in a PCT application, who is not the applicant of the US priority application, could assert the entitlement to priority during the European phase.

In the cases T 1513/17 and T 2719/19, leading to the referral, the Opposition and Examination Divisions found the priority claims invalid because not all the inventors listed in the U.S. priority application had assigned their priority right to the applicants of the respective European patent application before their filing.

Regarding the first question, the Enlarged Board of Appeal affirmed the EPO’s jurisdiction to assess the entitlement to claim priority under Article 87(1) of the European Patent Convention (hereinafter EPC).

In this determination, the Enlarged Board differentiated between the right to file a European patent application and the right to claim priority. Article 60(3) of the EPC restricts the EPO’s ability to adjudicate an applicant’s right over the patent application itself, which does not extend priority rights.

The Enlarged Board reasoned that without the capability to verify the validity of a priority claim, the EPO could not accurately determine the relevant state of the art for the period between the priority date and the filing of the subsequent application, impacting its ability to assess an invention’s patentability.

Moreover, the Enlarged Board stated that, the right to priority and its transfer are governed by the autonomous law of the EPC, independent of national legislations.

Regarding the second question, the Enlarged Board inferred that the entitlement to priority is presumed valid if the formal requirements for claiming priority are satisfied.

This presumption arises because (i) all parties involved typically benefit from an application’s priority claim, (ii) the EPC stipulates no formal requirements for transferring priority rights, and (iii) the applicant claiming the priority application must facilitate the subsequent application, for instance, by supplying unreleased documents like certified copies of the priority application.

The Enlarged Board established a “rebuttable presumption” that an applicant claiming priority entitled to do so. The presumption, subject to challenge, applies whenever the priority applicant differs from the subsequent one, irrespective of the subsequent application being a PCT application.

Furthermore, the Enlarged Board applied this rebuttable presumption to the situation at stake and considered the joint filing of a PCT application as indicative of an implied agreement between the applicants on the joint use of the priority right, barring evidence to the contrary.

Before this decision, when the entitlement to priority was challenged, some EPO decisions required the patent owner to prove a valid transfer of the right of priority.

With this ruling, the burden of proof is now inverted.

The burden of proof now lies with the party contesting the subsequent applicant’s right to priority to demonstrate the absence of such entitlement.