Tesla Inc Chief Executive Officer Elon Musk has sold nearly $13 billion worth of shares since early November when the world's richest person polled Twitter users about offloading 10% of his stake in the electric-car maker.

The billionaire sold another 934,091 shares for $906 million on Monday to pay for taxes on the exercise of stock options to buy 2.13 million shares in Tesla, according to US securities filings.

How did musk sell?

Musk said on Nov. 6 he would sell 10% of his stake if Twitter users agreed. He owned a combination of about 244 million shares through his trust and stock options, bringing his stake in Tesla to about 23% as of June 30.

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It included 170 million shares held by his trust.

The tweet was vague. Musk did not outline if he was intending to offload 10% of his shares he indirectly owned through the trust or if his stock options were also part of the deal.