Elon Musk has now sold more than half the stock he vowed on Twitter

Tesla shares have rebounded 9.4% after initially slumping following Musk's Twitter poll.

After a few days’ break, Elon Musk resumed selling shares in Tesla Inc., now coming more than halfway to making good on his promise to offload 10% of his stake in the electric-car maker.

The billionaire sold an additional 934,091 shares for $1.05 billion, according to regulatory filings late on Tuesday U.S. time. He also exercised 2.15 million stock options, and the sales were made to cover the taxes related to that transaction, the documents showed.

With the most recent disposals, Musk now has offloaded 9.2 million shares and collected about $9.9 billion of proceeds since he conducted a Twitter poll asking whether he should sell 10% of his Tesla stake. A chunk of that money will go to taxes.

To reach the 10% threshold, Musk would need to sell some 17 million shares, or about 1.7% of the company’s outstanding stock. If his exercisable options are factored into his overall ownership, he’d need to sell even more.

Musk has exercised millions of options since the Twitter poll, all of which were less than a year from their expiration date. In September, he established a pre-arranged trading plan to carry out “an orderly sale of shares related to the exercise of stock options,” filings show. The Nov. 6 Twitter poll didn’t disclose the existence of that plan.

Tesla shares have rebounded 9.4% after initially slumping following the poll. Its tokens on the FTX crypto exchange slipped to $1,102.70 as of 12:38 p.m. in Hong Kong Wednesday after closing at $1,109.03 in New York. 

Musk, 50, is the world’s richest person with a $303.7 billion fortune, according to the Bloomberg Billionaires Index. He’s added $133.9 billion to his net worth this year, more than anyone else, amid a 57% jump in Tesla shares.