The European Patent Office (EPO) has been a desirable venue for seeking patent protection in Europe. For instance, a patent application granted by the EPO can provide patent protection in many European countries, such as the United Kingdom, France, and Germany.
Many of the patent applications that are filed in the EPO seek the priority filing date of a previously filed patent application. In many instances, a U.S. provisional patent application may be filed in the United States Patent and Trademark Office. Within a year, an international patent application may be filed under the Patent Cooperation Treaty (PCT) that claims priority to the U.S. provisional patent application. Thereafter, the PCT application may enter national stage in the EPO and claim priority back to the U.S. provisional patent application.
In order for claims of priority to be valid in the EPO, various criteria must be satisfied. For instance, the subject matter disclosed in the European patent application must be fully disclosed in any priority patent applications.
In addition, the priority claim must be made by the identical legal person who filed the earlier priority application. If a different legal person makes the claim to priority, then they must be the successor in title of the priority applicant. An example of this requirement is illustrated below:
- A priority patent application (e.g., a U.S. provisional patent application) is filed in the name of A (e.g., an inventor); and
- A subsequent patent application claiming the priority of the U.S. provisional patent application (e.g., a PCT patent application or a European patent application) is filed in the name of B (e.g., the inventor’s employer).
For the priority claim to be valid, an assignment from A to B should have been carried out before the subsequent application was filed.
The position is not as clear in the situation where a U.S. provisional patent application is filed in the name of one or more employee inventors (but no other parties) and the subsequent patent application claiming the priority of the priority application is filed in the name of the inventor’s employer. It is possible that, because of an obligation to assign to the employer, there might be an ‘equitable’ assignment in place and that the priority claim is valid.
Nonetheless, in view of the above requirements, it is recommended that the rights of a U.S. provisional patent application be assigned prior to the filing of a PCT application or a European patent application. In addition, it is recommended that any subsequent PCT application (or other patent applications that may enter Europe) be filed in the name of the assignee of the U.S. provisional patent application.
 For a complete listing of the countries covered by the EPO, see: http://www.epo.org/about-us/organisation/member-states.html
Article 4(A)(1) of the Paris Convention