Requirements to Validly Prove An Entitlement to Claim Priority Before the EPO

By: Elsa Benveniste


In the recent decision T577/11, a Technical Board of Appeal of the European Patent Office (EPO) considered the issue of an entitlement to claim priority before the EPO, particularly when a transfer of a first patent application occurs before the filing date of a subsequent European application claiming priority on the first application.

As in previous decisions, the Board confirmed once again that for subsequent applications filed by someone other than the person who filed the priority application, a valid transfer of the right to claim priority or of the priority application must have already occurred when the later application was filed. Unfortunately, this requirement is sometimes overlooked, especially when the Applicant for the priority application is an inventor employed by the Applicant for the subsequent application and when the two Applicants belong to the same group of companies. Whenever the validity of the patent is challenged based on an intermediate European patent application published after the priority date but claiming an earlier priority date, the loss of a valid priority date may result in the refusal of the application or the revocation of the patent.

According to Article 87(1) of the European Patent Convention (EPC), the right of priority may be enjoyed both by the person having duly filed, in or for any state party to the Paris Convention or any member of the WTO, a European patent application and by any successor in title for the purpose of filing a European patent application in respect of the same invention within a twelve-month priority period. The EPO interpreted the reference to the successor in title in Article 87(1) EPC as requiring a transfer of the right of priority before the filing of the subsequent application (T 205/14).

In T577/11, the EPO confirms its established position with respect to the Applicant’s right to claim priority, particularly with regard to the impossibility of recognizing a retroactive transfer even when a national law would allow it.

In the case at issue, a patent assignment agreement between two distinct business entities of the same group was executed three days after the expiry of the priority period, and it included a retroactivity clause. The agreement read: “This Agreement has a retroactive effect to commence as from [more than nine months before expiry of the priority period]. As from the effective date the ASSIGNEE is considered the sole and exclusive owner of the Patents.” Thus, the question related to the retroactivity of the agreement, particularly with regard to the notion of transfer of “economic ownership” under national law, has arisen. The business entity wishing to acquire the patent rights was retroactively entitled to the profits and revenues of the transferred rights, but the business entity owning the patent rights remained the legal owner until the date of the agreement’s conclusion.

The Board decided that a succession in title that occurs after the filing date of the subsequent application is not sufficient to comply with the requirements of Article 87(1) EPC and that the applicant from the priority application and the applicant from the subsequent application contractually agreeing that (only) economic ownership of the priority application and the right to claim its priority is to be transferred to the subsequent applicant is not sufficient to consider the latter a successor in title within the meaning of Article 87(1) EPC.

In view of this and of previous decisions by the EPO Boards of Appeal, when filing a European application (be it a direct European application or a Patent Cooperation Treaty [PCT] application susceptible of entering the European regional phase) in the name of an Applicant B claiming priority from a previous application filed in the name of an Applicant A, to be on the safe side, the following is recommended:

  • Assignments should be in writing, and they should be signed and dated before the filing date of the subsequent European application because an assignment dated after the filing date cannot retroactively restore the right to claim priority.
  • The priority application should be identified in the assignment by application number, filing date, and country of filing since evidence may be required to “indubitably establish” that the transfer of the required priority rights has occurred.
  • Assignments should specifically state that not only the right to be granted the patent but also the right to claim priority is assigned because the right to claim priority from an application is considered distinct from the right to be granted a patent; thus, these two rights are considered independently assignable.
  • Assignments should be signed by both parties, i.e., by the assignee and assignor (Art. 72 EPC, decision T62/05 and Guidelines for Examination, November 2016 edition).

The above precautions must be taken even when Applicant A is an inventor employed by Applicant B and/or an agreement has already been entered obliging Applicant A to assign his or her rights in future patent applications to Applicant B; they should also be taken when Applicants A and B belong to the same group of companies.

If assignments meeting the above criteria cannot be obtained, then the European or the PCT application should be filed in the name of Applicant A. The rights in the European/PCT application may be assigned from Applicant A to Applicant B after the filing date of the application, thus preserving the right to claim priority.