{"references": ["Council Regulation (EC) No 1/2003 of 16 December 2002 on the implementation of the rules on competition laid down in Articles 101 and 102 of the Treaty, OJ L 1, 04.01.2003, pp.1-25.", "Council Regulation (EC) No 139/2004 of 20 January 2004 on the control of concentrations between undertakings, OJ L 24, 29.01.2004, pp. 1-22, in particular Articles 3(1) and 1(2) and 1(3). The Commission's exclusive jurisdiction to enforce the EU Merger Regulation derives from its Article 21.", "ECA (2001) The Exchange of information between members on multijurisdictional mergers. A procedural guide. Available from: https://ec.europa.eu/competition/ecn/eca_information_exchange_procedures_en.pdf [Accessed September, 12 2020].", "ECA (2005) Principles on the application, by National Competition Authorities within the ECA, of Articles 4 (5) and 22 of the EC Merger Regulation. Available from: https://ec.europa.eu/competition/ecn/eca_referral_principles_en.pdf [Accessed September, 12 2020].", "MWG, Best practices on cooperation between EU National Competition Authorities in merger review adopted November, 8 2011. Available from: https://ec.europa.eu/competition/ecn/nca_best_practices_merger_review_en.pdf [Accessed: September, 12 2020].", "EC (2011) Mergers: competition authorities agree best practices to handle cross-border mergers that do not beneft from EU one-stop shop review [Press release of November, 9 2011]. Available from: https:// ec.europa.eu/commission/presscorner/detail/en/IP_11_1326 [Accessed September, 12 2020].", "MWG, Best Practices on cooperation between EU National Competition Authorities in merger review adopted November, 8 2011, \u00a71.3.", "MWG, Best practices on cooperation between EU National Competition Authorities in merger review adopted November, 8 2011, \u00a71.3."]}

This unit was published in „International Cooperation of Competition Authorities in Europe: from Bilateral Agreements to Transgovernmental Networks” Błachucki, M., ed., (2020). Cooperation among Competition Authorities in multijurisdictional filings should always be a factor to take into consideration. The ECA Notice is a mechanism through which European Competition Authorities cooperate with each other when reviewing transnational merger transactions. Although active for almost 20 years, the ECA Notice cooperation mechanism is hardly well-known among stakeholders, in particular merging parties. Nevertheless, the ECA Notice cooperation mechanism has proven to be an extremely useful tool in promoting consistency and avoiding conflicting assessments and final decisional outcomes in EU national merger control. This, however, is not short of challenges. This article intends to provide a brief insight on how cooperation in multijurisdictional filings of merger transactions works in practice, the principles it is based on, and its benefits and challenges to both National Competition Authorities and merging parties.