China’s State Administration for Market Regulation (SAMR) fined Alibaba 18 billion yuan, or approximately 4 percent of the company’s 2019 revenues Friday, after a months-long investigation. This fine, the largest in the history of Chinese antitrust law, follows the unexpected interruption of Ant Group’s IPO in November. Ant Group is an affiliate company of Alibaba.

Although China’s anti-monopoly law provides 60 days for Alibaba to appeal SAMR’s administrative decision, the company released a letter Saturday accepting the fine and promising to increase internal compliance measures in order to comport with the antitrust law in the future.

In a press release on SAMR’s official WeChat account, the agency identified Alibaba’s “two for one” policy as being uniquely anticompetitive. In order for an online retailer to be listed on Alibaba’s platform, they must not open stores or participate in promotional activities on other platforms. SAMR found that this policy violated Article 17(1)(4) of the Anti-Monopoly Law, which prohibits companies restricting other retailers in this manner.

In addition to the administrative fine, SAMR requires the implementation of a plan to address future antitrust concerns. In addition to strengthening internal compliance protocols, Alibaba must take measures to protect the rights of consumers and businesses on its platform in the future and submit self-inspection reports to SAMR for the next three years.