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Right to priority in European Patent Applications - EPO decides there is a rebuttable presumption of validity


The Enlarged Board of Appeal at the European Patent Office (EPO) has now issued its written decision in consolidated cases G1/22 and G2/22. The Enlarged Board of Appeal concludes that the EPO is competent to assess priority entitlement and that there is a rebuttable presumption that an applicant claiming priority in accordance with the formal requirements under the EPC is entitled to do so.

Entitlement to priority ultimately stems from The Paris Convention, and one of the defining features is that the right to claim priority belongs to the same person or their successor in title. Issues around validity of the priority claim can thus arise where the priority application and a subsequent application have different named applicants. In such cases the right to claim priority must have been transferred to the applicant(s) of the subsequent application.

This issue arose during opposition and examination of two connected cases before the EPO. The priority applications for these cases were filed at the US PTO under US Patent law that, at the time, required patent applications to list the inventors as applicants. The European patent applications were derived from subsequent PCT applications that claimed priority to the US cases.  The PCT applications only listed the inventors as applicants for the purposes of any US application derived therefrom. The priority claims were found to be invalid by the EPO and the applicant appealed.  In considering the appeals (T1513/17 and T2719/19), the EPO's Technical Boards of Appeal decided that this point of law should be referred to the EPO's highest forum, the Enlarged Board of Appeal, for consideration.  In making the referral, it was also agreed that a separate question - whether the EPO was competent to decide on issues of priority, raised in the EPO's Technical Board of Appeal decision T844/18, should also be asked.

The Enlarged Board of Appeal was asked the following questions:

I. Does the EPC confer jurisdiction on the EPO to determine whether a party validly claims to be a successor in title as referred to in Article 87(1)(b) EPC?

If question I is answered in the affirmative:

II. Can a party B validly rely on the priority right claimed in a PCT application for the purpose of claiming priority rights under Article 87(1) EPC in the case where:

1) a PCT-application designates party A as applicant for the US only and party B as applicant for other designated States, including regional European patent protection and

2) the PCT-application claims priority from an earlier patent application that designates party A as the applicant and

3) the priority claimed in the PCT application is in compliance with Article 4 of the Paris Convention?

Regarding question I, the Enlarged Board rephrased the question as "Is the EPO competent to assess whether a party is entitled to claim priority under Article 87(1) EPC?" The Enlarged Board distinguished between the right to a European patent application and the right to claim a priority date. The EPO is not competent to assess an applicant's entitlement to file a European patent application. However, it was deemed that this does not extend to the right to claim priority, and so the EPO is competent to assess priority entitlement.

The Enlarged Board went on to discuss the purpose of a priority claim and the approaches to assessing validity of this taken in different jurisdictions. It acknowledged that the EPC did not set out any formal requirements that need to be met for proper transfer of a right to claim priority from the applicant of a priority application to that of a subsequent application. It concluded that the autonomous law of the EPC should not set higher formal requirements than those of any relevant national laws.

The Enlarged Board discussed the formal requirements for claiming priority under the EPC (such as providing a certified copy of the (unpublished) priority application), which the applicant would be unable to meet without support from the priority applicant. Such support is evidence that the applicant of the priority application "accepts or at least tolerates" the use of the priority by the subsequent applicant. The Enlarged Board therefore concluded that, where the formal requirements of the EPC for claiming priority have been met, there is a "rebuttable presumption" that the subsequent applicant has the right to claim the priority. This rebuttable presumption reverses the burden of proof such that the party challenging the entitlement must prove that the entitlement is missing.

Regarding the specific situations set out in question II, the Enlarged Board discussed the "PCT joint applicants approach", in which applicants for different designated states in a PCT application may enjoy a right of priority derived from a priority application filed by only one of the applicants. However, this was deemed to have no practical effect: the fact a PCT application had been jointly filed may serve as evidence that there is an agreement between the applicants to share the priority right such that all the applicants may enjoy a priority right acquired by only one of the applicants. A general decision on the viability of the PCT joint applicants approach was therefore deemed not needed. Furthermore, the concept of an "implied agreement" was also held to apply for a directly filed European application where at least one of the co-applicants was an applicant for the priority application.Evidence putting into question an implied agreement would have to be of a substantial nature.

The referred questions were therefore answered as follows:

I. The European Patent Office is competent to assess whether a party is entitled to claim priority under Article 87(1) EPC.

There is a rebuttable presumption under the autonomous law of the EPC that the applicant claiming priority in accordance with Article 88(1) EPC and the corresponding Implementing Regulations is entitled to claim priority.

II. The rebuttable presumption also applies in situations where the European patent application derives from a PCT application and/or where the priority applicant(s) are not identical with the subsequent applicant(s).

In a situation where a PCT application is jointly filed by parties A and B, (i) designating party A for one or more designated States and party B for one or more other designated States, and (ii) claiming priority from an earlier patent application designating party A as the applicant, the joint filing implies an agreement between parties A and B allowing party B to rely on the priority, unless there are substantial factual indications to the contrary.


It is no longer a requirement for US applications to be filed in the name of the inventors, and so remaining European cases having circumstances similar to the referring decisions will be few in number. However, this Enlarged Board Decision indicates a less rigid approach to requiring formal evidence of a transfer of priority right before a subsequent application is filed. Nevertheless, our recommendation remains to ensure that there is a written transfer of the right to claim priority dated before the filing of the subsequent application in any case where the applicants for the priority application and the subsequent application differ. 

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