Section F‑IV, 3.5 in the Guidelines for Examination in the EPO applies mutatis mutandis.
The EPO allows multiple dependent claims, provided that they do not detract from the clarity of the claims as a whole and that their arrangement does not create obscurity in the definition of the subject-matter to be protected. The EPO applies option GL/ISPE A5.16 of the Appendix to Chapter 5 of the ISPE Guidelines.
In case of unclarity, it may be appropriate for the examiner to first invite the applicant to provide informal clarification before the search is carried out (see GL/PCT‑EPO B‑VIII, 3.3-GL/PCT-EPO B-VIII, 3.6).
See GL/PCT‑EPO F‑IV, 3.7 for claims referring to a claim in a different category.