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Assigning priority rights in Europe – How to stay out of trouble

1 December 2017

At first glance, it seems straightforward to assign intellectual property rights from one entity to another.  A recent decision by the EPO’s Board of Appeal in T1201/14 (see here) shows that it can, and relatively often does, go wrong.

According to European jurisprudence it is generally accepted that the right to claim priority arising from a patent application is transferable independently from the corresponding title to the patent application itself and may be transferred individually for every country and to a number of different parties.  What’s more, as this case confirms, the established interpretation of Article 87 EPC requires that the right to priority must be assigned to the relevant party before filing any subsequent patent applications.

However, the provisions of the EPC do not lend themselves to an autonomous determination of the formal requirements for assignments, which have been considered in previous decisions to be a matter of national law.  In this case the patent proprietor tried to use this aspect to their advantage.  In detail, the patentee argued that although they had not transferred the right to priority explicitly in a written contract before the date of filing of the European patent application, their priority claim was still valid, since:

  1. The priority application was filed in the US, and US national law allows for retrospective assignments of the right to priority; or
  2. Germany is a designated member state of the European patent in question, and under German national law there is no requirement for the transfer of the right to priority to be made in writing, and so an oral or implicit transfer is sufficient; and/or
  3. Since the Assignor has it’s residence in Taiwan, Taiwanese law should be applied, which does not make any distinction between the “right to the priority founding registration” and the “right to claim priority” therefrom. Furthermore, similar to German law, Taiwanese law provides for the possibility of an implicit transfer of the right to priority without the need for a written contract.

While the Board accepted that there is no established jurisprudence of the Boards of Appeal as to which national law is generally applicable, they did not find any of the above arguments persuasive. In this regard, the Board ruled that even if all of the above national laws could be applied, this could not remedy the fact that the patentee failed to timely transfer the right to priority. Referring to the above numbering, the Board found:

  1. Although retrospective assignments are allowed under US national law, this is not compatible with established European Case Law and hence cannot be acknowledged by the EPO;
  2. While the Board agreed that an implicit or oral contract may be considered sufficient for a timely transfer of the right to priority, it could not be established “beyond reasonable doubt” that an implicit transfer of the right to priority had occurred before the date of filing;
  3. Regarding the two rights being inseparable in Taiwan, the Board concluded that this is not compatible with established European Case Law and hence cannot be acknowledged by the EPO. In terms of the implicit transfer, the Board noted that the evidence provided “prima facie” failed to prove “beyond reasonable doubt” that a transfer of the right to priority occurred, similar to the reasoning relating to German law.

Although the Board of Appeal did not establish which national laws could or should be applied to the transfer of priority rights, there are some practice points we can take home from this decision.

Firstly, the right to priority for a European patent application must ALWAYS be transferred before the filing date, even if under an applicable national law retrospective assignment of the right to priority is permissible.  Secondly, the principle that the right to the priority application and the right to claim priority are separate rights, cannot be circumvented by the argument that the applicable national law does not foresee an independent priority right.  Thirdly, if the applicable national law allows for verbal contracts and implicit transfer of rights, there is a chance that valid transfer of the right to priority can be proven even if no written contract is available BUT the burden of proof is on the party claiming that the transfer took place, and they must establish this “beyond reasonable doubt”.  Witness statements that are not contemporaneous may not suffice.


Frank Harner
Advanced Engineering group

If you require further information on anything covered in this briefing, please contact Frank Harner (; 44 20 7940 3600) or your usual contact at the firm. This publication is a general summary of the law. It should not replace legal advice tailored to your specific circumstances.

© Withers & Rogers LLP, December 2017