At the search stage, the search division dealing with the question of unity applies the same criteria as in substantive examination (see F‑V). In particular, it will not raise an objection of lack of unity merely because the inventions claimed are classified in separate classification groups, or merely for the purpose of restricting the search to certain sections of the documentation, for example certain classification groups (but see B‑V, 3.3).

The assessment of unity cannot be made once and for all. Normally, the search division will develop a first view even before it carries out the search. This first assessment is necessarily made in a prima facie manner, on the basis of general knowledge and the statements of prior art contained in the application. During and after the search the assessment is reconsidered in the light of the documents found. The beginning of substantive examination is a further procedural step where the previous findings on unity are reconsidered. Even later in the proceedings the position adopted previously may be superseded in view of new facts and evidence.

As a general rule, a previous position on unity of invention is maintained unless strong reasons exist which lead to a situation where the position must be changed. The final decision on the question of unity of invention is taken by the examining division or, ultimately, the competent board of appeal. Therefore, as a matter of principle, any previous finding on unity is open to review.