Berkshire Hathaway bought $1 billion in shares of Brazilian digital bank Nubank in the fourth quarter of 2021, according to a 13F SEC filing.

In December 2021, when Nubank went public, Berkshire Hathaway reportedly acquired 30 million shares for a total of $250 million. At that time, Nubank's valuation reached $41.5 billion.In the fourth quarter of 2021, Berkshire also sold 1.27 million shares of VISA and 302,000 shares of Mastercard.In June 2021, Berkshire Hathaway invested $500 million in Nubank by leading the extension of a Series G funding round.Although Nubank does not allow trading in cryptocurrencies, its investment unit, NuInvest, allows users to invest in crypto ETFs, according to the company website.In 2018, Berkshire Hathaway CEO of Warren Buffett called bitcoin "rat poison squared."