While the majority of jurisdictions agrees on the need for a competition law to have a merger control regime, many differences still exist on the scope of the agencies’ merger review powers. One of these areas of divergence is the ability of competition authorities to review and remedy the anticompetitive effects of consummated mergers. Some jurisdictions, beyond those with a voluntary notification system, which allows parties to close a transaction without prior clearance from the competition authority, have the power to review consummated mergers and to impose remedies in cases such mergers result in a significant lessening of competition.

In cases where consummated mergers can be reviewed, the selection and evaluation criteria used by agencies to prioritise and perform their investigations, as well as an analysis of the implications for business of the competition authorities’ powers to investigate consummated mergers are fundamental. Important questions arise in relation to designing effective remedies for consummated mergers with an anti-competitive effect.

In June 2022, the OECD held a roundtable that discussed the existence and need of legal powers to review consummated mergers as well as their scope and elements that are relevant for their analysis such as the appropriate time perspective of the review; the use of post-merger data and information; and the utility of interim measures and hold separate agreements.

From the discussion, it was clear that these powers have proven useful in specific circumstances, such as transactions in small jurisdictions. Moreover, it was noted that the shorter the delay between a transaction and its review, the less troublesome the assessment becomes. Finally, it was concluded that when powers to review consummated mergers are available, there is a need for clear guidance on the criteria to use them, including the timeframes and the utility of ex post information.

All related documentation will become available on this page. 

See the full list of best practice roundtables on competition.

Jonathan Kanter Bio 
Assistant Attorney General, Antitrust Division, US Department of Justice

John Kwoka Bio
Professor of Economics, Northeastern University

Aviv Nevo Bio  
Professor, George A. Weiss and Lydia Bravo Weiss, University of Pennsylvania

Fiona Carlin Bio  
Partner and Chief Executive, EMEA+ Region, Baker McKenzie

OECD Secretariat

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OECD Background Note  l  Version française

Detailed summary of the discussion EN / FR

Executive summary with key findings EN / FR

Contributions from delegations

Ex Ante Regulation and Competition in Digital Markets (2021)

Start-ups, Killer Acquisitions and Merger Control (2020)

Gun jumping and suspensory effects of merger notifications (2018)

Investigations of Consummated and Non-Notifiable Mergers (2014)

Remedies in Merger Cases (2011)

Merger Remedies (2003)

OECD best practice roundtables on competition

More OECD work on competition