(124) If the processing of personal data takes place in the course of the activities of an organizational unit of the controller or processor in the Union, and the controller or processor has organizational units in more than one Member State, or if the processing, which takes place in the course of the activities of a single organizational unit of the controller or processor in the Union, significantly affects or is likely to significantly affect data subjects in more than one Member State, the lead authority should be the supervisory authority of the main organizational unit of the controller or processor or of the single organizational unit of the controller or processor. It should cooperate with the other authorities concerned on the grounds that the controller or processor has an organizational unit on the territory of their member state, that there is a significant impact on data subjects residing on that territory, or that a complaint has been filed with those authorities. Also in cases where a complaint has been filed by a data subject who is not resident in that Member State, the supervisory authority to which the complaint has been filed should be considered the supervisory authority concerned. As part of its task of issuing guidelines on the application of this Regulation, the European Data Protection Board should be able to issue guidelines in particular on the criteria to be taken into account to determine whether data subjects are significantly affected by processing in more than one Member State, and on what constitutes a relevant and legitimate objection.