Nov 15 (Reuters) - Tesla (TSLA.O) CEO Elon Musk has sold $930 million in shares to meet tax withholding obligations related to the exercise of stock options, U.S. securities filings showed on Monday. Musk sold 934,091 shares after exercising options to buy 2.1 million stocks at $6.24 each on Monday. Tesla shares closed at $1,013.39. He is required to pay income taxes on the difference between the exercise price and fair market value of the shares.This is the second time in a week that the billionaire has exercised his stock option. Last Monday, he sold another 934,000 shares for $1.1 billion after exercising options to acquire nearly 2.2 million shares. read more The two options-related sales were set up in September via a trading plan that allows corporate insiders to establish preplanned transactions on a schedule, the filings said. As of the end of 2020, he had an option to buy 22.86 million shares, which expire in August next year, a Tesla filing shows. On Nov. 6, Musk polled Twitter users about selling 10% of his stake, pushing down Tesla"s share price after a majority on Twitter said they agreed with the sale. It was not clear how or whether the trading plan related to Musk"s Twitter poll.