Tesla Chief Executive Elon Musk told the electric car company that he plans to purchase $20 million of common stock during the next open trading window, according to a filing related to the CEO's settlement with the Securities and Exchange Commission.

"Separate and apart from the settlement, Elon has notified Tesla that he intends to purchase from Tesla, and Tesla expects that it will issue and sell to Elon, $20 million of Tesla's common stock during the next open trading window at the then-current market price," the filing read.

Tesla shares fell 1 percent Wednesday morning following the filing. Musk is the largest shareholder in Tesla, holding more than $9 billion worth of the stock or more than 33 million shares before Wednesday's announcement. The CEO bought $24 million worth of Tesla in June and $9.9 million in May, according to InsiderScore.com.

Tesla shares are down 10 percent in 2018.

The 8-K filing also detailed Tesla and Musk's settlement with the SEC. A judge approved the settlement with the SEC on Tuesday over allegations that Musk committed fraud when he tweeted earlier in the year that he had secured necessary funding to take the automaker private.