1.4 Assessment and possible review of the unity requirement 

A search division dealing with unity at the search stage applies the same criteria as are used in substantive examination (see F‑V). In particular, it will not raise an objection of lack of unity merely because the inventions claimed are classed in separate classification groups, or simply as a way of restricting the search to certain parts of the documentation, for example certain classification groups (but see B‑V, 3.3).

The assessment of unity at the search stage is not definitive. Normally, the search division will have formed a first impression even before it carries out the search, but it will necessarily have done so prima facie, based on the common general knowledge in the relevant field and the prior art mentioned in the application. It will revisit this initial assessment during and after the search in the light of the documents found. Its findings will be reviewed again when substantive examination begins and even the position taken then may be changed later on in the proceedings in the light of new facts and evidence.

However, as a general rule, a position already taken on unity of invention is maintained unless there are sound reasons for changing it. The final decision on the matter is taken by the examining division or – in the event of an appeal – ultimately by the board of appeal. So any previous finding on unity is basically always open to review.