Elon Musk is being sued by the SEC over Twitter-related securities violations

US securities regulators sued Elon Musk in federal court in Washington on Tuesday in an enforcement action stemming from his $44 billion purchase of Twitter, now called X.

The lawsuit against Mr. Muska, who has become a close adviser to President-elect Donald J. Trump, is likely to be one of the most contentious final actions by the Securities and Exchange Commission under Gary Gensler, its outgoing chairman.

The SEC claims that when buying Twitter in 2022, Mr. Musk violated securities laws by amassing a large equity position in the company without filing proper notice. The complaint said he waited 11 days before filing the requested statement with the SEC

Regulatory documentation is needed so that investors in the market can monitor the moves of large investors and potential takeover bids.

During the past few weeks, Mr. Musk mocked the SEC in posts on X about the possibility of a lawsuit. In December, he shared a letter his lawyer sent to the agency, rejecting a settlement offer in the case.

This is the third time the SEC has gone to court with Mr. Muskom, and the first case was initiated by securities regulators during the first mandate of Mr. Trump. That lawsuit stemmed from inappropriate market-driving posts that Mr. Musk has announced his thoughts on taking his electric car company, Tesla, private.

Before filing the suit on Tuesday, the SEC went to court to force Mr. Muska to comply with the subpoena that demanded his statement be taken.

Since Mr. Gensler leaves office with the inauguration of Mr. Trump on Monday, it is unclear whether regulators will proceed with the lawsuit. Mr. Trump has said he intends to nominate Paul Atkins, a former SEC commissioner and pro-business conservative, to succeed Mr. Gensler.

This is a developing story. Check back for updates.