" Berkshire is carrying the Kraft Heinz stake for $13 billion under the equity method of accounting since it owns more than 20% of the company. Under that 20% level, Berkshire would carry the stake at market value.

In its third quarter 10-Q, Berkshire said it had examined the Kraft investment and determined that “recognition of an impairment charge in earnings was not required.” Berkshire also performed a similar test of its equity investment in Occidental Petroleum equity—also carried under a similar accounting—and found no impairment was required.

Berkshire could take an impairment charge on the Kraft Heinz investment when it reports its fourth-quarter earnings on Feb. 22. Any impairment charge would be noncash and therefore would probably be ignored by investors. Berkshire already took a $2.8 billion non-cash impairment of the Kraft Heinz stake in 2018."

msn.com - Berkshire is losing money on its billion kraft heinz stake impairment is possible

I expect a write down in Flying J as well.