The Commission must give the persons and undertakings concerned the opportunity, at every stage of the procedure, of making known their views on the objections against them (Regulation No 139/2004, Article 18). Article 14 of Regulation No 802/2004 specifies the rules applicable to the hearing of the notifying parties. The notifying parties who have so requested in their written comments, may thus be heard by the Commission in a formal oral hearing, where the EU authority intends either to take a final decision, or to impose a fine. The right to be heard falls within the scope of the Commission’s initiative at other stages of the procedure. Other involved parties may be heard under the same conditions. The Commission is not required to draw up minutes of hearings.

The right to be heard, at every stage of the merger control procedure, is also open to third parties, i.e. natural or legal persons who are incidentally affected by the decision, provided they demonstrate a sufficient interest (Regulation No 802/2004, Article 16). The status of third party has been admitted for competitors of the merging parties, institutions representing the staff of the undertakings concerned, members of the administrative or management bodies of the undertakings concerned, or consumer associations, where the proposed merger concerns products or services used by final consumers (Regulation No 802/2004, Article 11). However, third parties do not enjoy identical guarantees to those given to the interested parties. They must submit a request to be heard in writing. In response the Commission informs them in writing of the subject-matter and nature of the proceedings and fixes a time-limit to make known their views. Only the request for hearing, and not the request for information, creates an obligation of information imposed on the Commission.