Documents submitted by Berkshire Hathaway to the U.S. Securities and Exchange Commission on September 27 local time show that the company sold a total of 11,678,366 shares of Bank of America common stock from September 25 to 27, with a total value of approximately 0.46 billion US dollars.

Through over a dozen sales, Warren Buffett has reduced his stake in Bank of America to a critical regulatory threshold, at which he will no longer need to promptly disclose his trading activities to the public.

A regulatory filing shows that his Berkshire Hathaway company, after the latest 10-week round of sales, currently holds about 10.3% of the bank. If he continues on this path, his stake will drop below 10% in about a week, thereby exempting him from immediate disclosure of the transactions. Once Berkshire's holding falls below this level, it can switch to providing quarterly updates.

Since mid-July, Buffett's total sales of Bank of America shares have reached 9.4 billion dollars. Nevertheless, based on last Friday's closing price, Berkshire's remaining stake in the bank is valued at nearly 32 billion dollars, making it still the largest shareholder of Bank of America.