Elon Musk has sold his first block of Tesla shares since 2016, exercising some stock options and then selling a portion of that to raise the cash he’ll need to pay taxes on the shares he acquired.

After making a promise on Twitter, Musk has sold about 4.5 million shares, raising over $5 billion.

The sales, disclosed in 10 regulatory filings late Wednesday, amount to about 3% of Musk’s stake in the company.

About $1.1 billion will go toward paying tax obligations for stock options granted to Musk in September.

Last weekend, Musk said he would sell 10% of his holdings in the company, worth more than $20 billion, based on the results of a poll he conducted on Twitter. The sale tweets caused a sell off of the stock Monday and Tuesday, but it recovered some on Wednesday. The shares were up 2.6% to $1,096 in extended trading Wednesday, and they have risen more than 50% this year.

The filings also disclosed that Musk exercised options to buy just over 2.1 million shares for $6.24 each. The company’s stock closed Wednesday at $1,067.95 per share.

The tax transactions were “automatically effected” as part of a trading plan adopted on Sept. 14 to sell options that expire next year, according to forms filed with the SEC. That was nearly two months before he floated the idea of the sale on Twitter.

After the transactions, Musk still owns about 167 million Tesla shares.

The options he exercised were about 9% of those he will need to exercise by August of 2022, or the option to purchase them will expire. But exercising those shares will result in a $1 billion federal tax bill, under the top federal income tax rate of 37%, with another 3.8% net investment tax on top of that.

He also will face an unknown amount of state income taxes in California, even though he has relocated to Texas, where there is no state income tax. California has a top state income tax rate of 13.3%.

While Musk conducted a well-publicized Twitter poll over the weekend asking his fans if he should start to sell shares, the real motivation for the sale of stock was “solely to satisfy [Musk’s] tax withholding obligations related to the exercise of stock options,” the filing said.

While the need for Musk to sell shares to pay taxes had been known by investors, shares of Tesla fell following the Twitter poll as some investors took it to mean he intended to sell more shares than had been expected. The share price also could have fallen Monday partly because of Musk’s sales of nearly 1 million shares that took place that day.

But Wednesday night’s filing suggests that Musk is not looking to sell all 22.9 million shares he will acquire when he exercises the options between this week and next August.

He apparently plans only to sell the minimum amount of shares necessary to pay taxes at the time he excercises blocks of options. His holdings of Tesla shares increased by 1.2 million shares, the difference between the number of shares he acquired and the number he sold. Shares of Tesla rose 2.7% in after-hours trading following the filing.

He already owned 170.5 million shares outright before this transaction, worth $182 billion based on Wednesday’s close. And even after exercising the options this week, he has already qualified for unexercised options to buy an additional 71.4 million shares, including the remaining 20.7 million options due to expire in August 2022.

He made a nifty $2.5 billion profit on the share purchases he made, since he only had to pay $6.24 per share to buy each share under the terms of the 2012 option, which is what Tesla shares cost at that time on a split-adjusted basis. And the shares he acquired were worth $1,180, based on the average selling price of the shares he sold.

But the $2.5 billion profit is only a small fraction of his net worth. His net worth, as calculated by Bloomberg, is nearly $300 billion, making him the richest person on the planet.

A $2.5 billion profit to someone worth $300 billion is the equivalent of the typical US household earning just over $1,000 on a sale of stock it already owned. The Federal Reserve’s most recent estimate puts median US household net worth at $121,700.

Most of Musk’s net worth is his Tesla shares and options to buy additional shares. Tesla became only the sixth company to ever be worth $1 trillion two weeks ago. But he is also the primary shareholder in privately held SpaceX.

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