In application of the discretionary powers principle, the Commission alone can decide to initiate an investigation and may freely choose the investigative measure to be taken. It can conduct inquiries by sector of the economy (Article 17 of Regulation No 1/2003); this type of measure, which enables it to gather information before initiating proceedings of its own motion for suspected infringements, is only rarely used. It may send requests for information to the governments and competent authorities of the Member States and to undertakings and associations of undertakings (Article 18 of Regulation No 1/2003) and may conduct all necessary inspections of undertakings and associations of undertakings (Article 20).

The Commission may, due to the autonomous nature of those measures, use them in the order that it wishes. It can apply the measure it considers the best suited to the search for evidence of the alleged violation. Requests for information and inspections are independent investigative procedures. Even if it already has evidence, or indeed proof, of the existence of an infringement, the Commission may legitimately take the view that it is necessary to request further information to enable it better to define the scope of the infringement, to determine its duration or to identify the circle of undertakings involved. It may also initiate a new inquiry in order to verify or supplement information which it obtained during a previous investigation.