Double Patenting In The EPO

The issue of "double patenting" arises in the EPO when one applicant files two European patent applications with closely related claims and the same effective filing date. Two situations where double patenting commonly needs to be considered are:

• when the claims of a divisional application overlap with the claims of its parent application; and
• when a first European patent application claims priority from a second European patent application and the claims of the first application overlap with the claims of the second application.

Under such circumstances it is necessary to determine how much overlap between the claims of the two applications should be permitted. The case law has developed such that the EPO will generally allow substantial overlap between the claims.