1.2.2 Cascading non-unity 

If a European patent application is found to lack unity at the search stage, the invention first mentioned in the claims (see F‑V, 3.4) will be searched and the applicant will be invited to pay further search fees for the others. They will also be warned that, even if a lack of unity "a posteriori" is later detected, no further invitation to pay additional fees will be issued.

If the applicant pays further search fees for any of the other inventions, a search is carried out for those inventions.

If this further search reveals that one or more of these inventions also lack unity "a posteriori", only the first invention in each group of inventions is searched. The applicant will not be invited to pay another set of further search fees.

The search division will draw up the search opinion, setting out the reasons for its finding of non-unity and giving an opinion on the patentability of the searched inventions (see B‑XI, 5).

Divisional applications can be filed for any inventions that have not been searched (see C‑IX, 1.2).

Example

The search division raises a lack of unity objection and identifies four different inventions A, B, C, D. The first invention A is searched and the applicant is invited to pay further search fees for inventions B, C and D. The warning mentioned above is given.

The applicant pays two further search fees for inventions B and C. During the further search, B is found to lack unity "a posteriori" and is divided into groups of inventions B1, B2 and B3.

In this case only B1 and C are searched. The European search opinion must fully explain why the claims of the application were divided into A, B, C and D and why B was then subdivided into B1, B2 and B3 and offer a view on whether A, B1 and C are patentable.

Examination of the application in the European phase will be based on either A, B1 or C (see C‑III, 3.2.2). The claims relating to inventions B2, B3 and D can be filed as divisional applications (see C‑IX, 1.2).