A valid priority claim can have a crucial effect on patentability, as illustrated by the ongoing CRISPR cases.  A failure to take into account national differences regarding the right to claim priority can therefore have dramatic consequences.  Here are some guidelines on best practice to avoid priority pitfalls.

A typical patent strategy involves the filing of an initial patent application in a single country and and the subsequent filing of a later application, such as an International application, claiming priority from the initial application. However, the initial application is not necessarily filed in the same name as the later application and this can affect the validity of a priority claim.

Due to differences in national laws around the globe, there is a risk that despite complying with local national law regarding priority, an applicant may fail to comply with the laws of other countries and hence lose his right to priority in those countries. An example of a recent decision by the European Patent Office highlighting the pitfalls in this area is discussed here.

The International Federation of Intellectual Property Attorneys (FICPI) has conducted an extensive survey of the various national requirements regarding priority and the results may be accessed here and more recent guidelines were published here.

Despite national differences, applicants can follow a simple common principle to ensure that their priority claim complies with all national laws:

The right to claim priority must be possessed by the applicant of the later application at the time of filing in order to enable the grant of a patent with a valid priority claim.

This principle can be translated into the following key guidelines, which are already our standard practice, but which we want to remind applicants of :

If possible, try to ensure that any later application is filed in the name of the applicant of the priority application.  This applicant should ideally also be the owner of both the invention and the priority rights at the time the later application is filed.

Alternatively, if the rights to the application, to the invention and to the priority claim belong to different parties, try to ensure that the rights to the application, to the invention and to the priority claim are transferred to the applicant prior to filing the later application.

Where it is not possible to ensure that rights to the invention and priority rights are possessed by the same party at the time of filing a later application, consideration should be given to naming as applicants all parties possessing rights in the invention and priority rights.

More detailed recommendations are set out in the FICPI guidelines, or contact one of our attorneys for further guidance.


“The priority right cannot typically be acquired retroactively to permit the grant of a patent with a valid priority claim in respect of a later application filed without such priority rights.”