Musk is expected to sell $18 billion in Tesla stock by the end of the year

On December 15, Tesla CEO Elon Musk sold $906 million worth of Tesla stock on Monday, which put him one step closer to his ultimate sales goal.

According to a Poll conducted by Musk on Twitter in November, he plans to sell a 10% stake in Tesla. At the time, he had slightly more than 170 million shares of Tesla stock, so theoretically he planned to sell about 17 million shares to make good on his promise on Twitter.

According to investment research firm InsiderScore/Verity, as of Tuesday morning, he had sold a total of 11.9 million shares involving 680 transactions totaling about $12.7 billion. Based on his goal of selling 10 percent of his stake, he is likely to sell another 5 million shares, which would be more than $4.8 billion at Tesla's closing price of about $966 on Monday. However, Musk may end up selling more shares. Currently, he is doing two kinds of stock sales: one to pay taxes for the exercise of options, and the other to cash out directly.

Under the goal of selling 10% of the shares, Musk may only sell another $5 billion before the end of the year. However, if he has other cash plans or needs, sales may be higher.