Elon Musk is selling massive amounts of Tesla shares

Elon Musk takes his Twitter polls seriously.

Following a poll in which he asked whether he should sell 10 percent of his Tesla stock, which ended with roughly 58 percent of users voting yes, Musk is following through. According to new filings with the Securities and Exchange Commission, Musk has sold roughly 4.5 million shares this week, with the total value exceeding $5 billion.

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Musk owns 170.5 million Tesla shares and has an option to buy 73.5 million more. It's unclear whether he's including the optioned shares when calculating his 10 percent goal, but either way he still needs to sell quite a few more to reach it.

When he posted the poll, Musk said that he would be selling the stock in order to pay tax (he doesn't take a salary so – according to Musk – the only way for him to pay tax on his gains is to sell stock).

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However, there may be another reason why Musk is suddenly so keen to sell stock and pay tax. According to CNBC, Musk is facing a $15 billion tax bill in the coming months on his stock options, meaning that he'd probably have to sell some of his Tesla stock anyway to pay that bill. There's also the convenient fact that Tesla stock was at an all-time high of roughly $1,220 when he posted his Twitter poll (the price fell roughly 17 percent following the poll).

Regardless of whether it was the will of the Twitterverse or looming tax bills that made Musk sell his stock, he'll have to pay 54.1 percent in taxes on the proceeds from the sale. It'll be interesting to see how Musk spends the rest, given that he typically doesn't have a lot of cash, and mostly lives on borrowed money.