“You know, Berkshire is subject to the 15% corporate alternative minimum tax. And if they don't pay an effective tax rate more than 15% in cash taxes over a three year running period, they will be taxed on their unrealized gains.”
From The Morning Filter: Berkshire Hathaway After Warren Buffett: An Early Read on What Investors Can Expect, Mar 5, 2026
https://podcasts.apple.com/us/podcast/berkshire-hathaway-after-warren-buffett-an-early/id1792280057?i=1000753375746&r=990
This was in an interview with Gregg Warren who covers Brk at Morningstar
as to a partial reason for selling.