3.2.3 Dependent claims 

A dependent claim and the higher-ranking claim on which it depends cannot be grouped into two different groups of inventions (see F‑V, 2.1).

If, however, the higher-ranking claim appears not to be patentable, then the question of whether there is still an inventive link between all the claims dependent on that higher-ranking claim needs to be carefully considered.

In this context it is important to verify that a claim that is drafted as a dependent claim is in fact a true dependent claim comprising all the features of the corresponding independent claim, see F‑IV 3.7. For a definition of a dependent claim, see F‑IV, 3.4 and 3.8.