Berkshire Hathaway owns 60 companies outright, taking them private through acquisition. Buffet didn't make his insane annual returns by controlling public companies, he did it by owning companies outright and shuffling capital from one to the other. There is only one tax return for 60+ companies, filed by Berkshire Hathaway.
Berkshire's investment in public stock (Coca Cola, Wells Fargo, etc) is mainly through investment of insurance float by its subsidiaries.
The myth that Berkshire Hathaway made its money by controlling publicly-traded companies is common. In fact, it is antithetical to Buffet's operating style. He is beholden to no one. If you want to share in his success you have to buy BRK.B and wait for long-term capital gains; you can't buy into his companies individually.