If in response to the search opinion the applicant does not restrict the application to a single invention searched, the objection of lack of unity raised at the search stage will be reviewed and if the examiner considers that it remains valid, a first communication repeating the lack-of-unity objection raised in the search opinion will be issued.
If the applicant does not restrict the application at all, or does restrict it, but still maintains two or more inventions, the application can be refused under Art. 82 (subject to the applicant's rights under Art. 113(1) and Art. 116(1)).
If the claims have not been simply restricted, but have instead, or additionally, been amended, such amendments can often result in the previously raised lack-of-unity objection no longer being valid, or in the arguments on which the objection was based no longer being complete. Such amendments would thus result in the objection having to be either withdrawn or at least newly argued.
Sometimes lack of unity of invention arises only during substantive examination, for example following an amendment of one or more claims so as to overcome an objection of lack of inventive step. In such situations the examiner should raise an objection, but only in very clear cases. If the examiner raises such a new lack-of-unity objection at this stage, this qualifies as a new objection which would start the 24-month period for filing a divisional application according to Rule 36(1)(b) (see A‑IV, 184.108.40.206).