Warren Buffett Secretly Building $100B+ Stake, Likely in Mitsubishi UFJ

Warren Buffett's Berkshire Hathaway has been granted confidential treatment by the SEC regarding one or more stock holdings, meaning Buffett is secretly building a position.

Based on the amount spent on equity securities in recent quarters and Berkshire's tendency to buy 5% stakes, this confidential stock likely has a $100B+ market cap.

Cost basis increases in "banks, insurance and finance" holdings point to the confidential stock being in the financial sector, narrowing it down to 13 possible companies.

By eliminating unlikely candidates based on Buffett's investing history, the most probable confidential buy is Mitsubishi UFJ Financial Group (MUFG).

MUFG meets Buffett's investing criteria - reasonable valuation, high quality, and ties to another Berkshire holding, Morgan Stanley - making it the most logical confidential buy.