Lack of unity is not a ground of revocation in later proceedings. Therefore, although the objection is certainly made and amendment insisted upon in clear cases, it is neither raised nor insisted upon on the basis of a narrow, literal or academic approach. This is particularly so during search when the possible lack of unity does not necessitate a further search.

When a lack of unity is established, the claimed subject-matter is divided into separate inventions and/or inventions grouped together in view of their technical relationships (see F-V, 3.2), i.e. according to any common matter comprising same or corresponding potential special technical features. In this context, an invention must have technical character and be concerned with a technical problem within the meaning of Art. 52(1) (see G‑I, 1 and G-I, 2), but it does not necessarily need to meet other requirements for patentability, such as novelty and inventive step (see G‑VI and G‑VII).

Lack of unity may be evident a priori, i.e. prior to carrying out a prior-art search, or may become apparent a posteriori, i.e. after taking into account the prior art revealed by the search in terms of novelty and inventive step.