On 4 September 2014, the Court of Justice handed down its judgment in the fasteners cartel (Case C-408/12 P). Although most of the appellants' claims were rejected, the Court recognised that the Commission, followed by the General Court ("GC"), had erred in law as regards the calculation of the fine imposed.

In 2007, the Commission found that YKK Stocko participated in a cartel in the fasteners sector for a period of more than nine years. During this period, YKK Stocko was acquired by YKK Corp and YKK Holding. The Commission held the new parent companies jointly and severally liable for the infringement for the part of the fine imposed on YKK Stocko after the acquisition. However, in determining the 10% turnover upper limit of the fine imposed solely on YKK Stocko for the period before the acquisition, the Commission used the consolidated turnover of the YKK group.

The Court of Justice held that the concept of an "undertaking participating in the infringement," for the purposes of Article 23(2) Reg. 1/2003, must necessarily be the same as for the application of Article 101 TFEU. An undertaking cannot be held responsible for infringements committed independently by its subsidiaries before the date of their acquisition. While the Commission correctly attributed responsibility, it failed to draw the necessary conclusions as regards the application of the 10% upper limit. The Commission, in calculating the fine, must take account of the specific turnover of the acquired undertaking rather than the entire group in order to apply the 10% upper limit.

Therefore, the Court of Justice reduced the part of the fine attributed to YKK Stocko, calculating it solely based on 10% of the YKK Stocko turnover.