From page K-58 of the 10-K, on the effect of the 'alternative minimum tax on book profits' on Berkshire:

On August 16, 2022, the Inflation Reduction Act of 2022 ('the 2022 act') was signed into law. The 2022 act contains numerous provisions, including a 15% corporate alternative minimum income tax on 'adjusted financial statement income', expanded tax credits for clean energy incentives and a 1% excise tax on corporate stock repurchases. The provisions of the 2022 act become effective for tax years beginning after December 31, 2022. On December 27, 2022, the IRS and Department of Treasury issued initial guidance for taxpayers subject to the corporate alternative minimum tax. The guidance addresses several, but not all, issues that needed clarification. The IRS and Department of Treasury intend to release additional guidance in the future. We will continue to evaluate the impact of the Act as more guidance becomes available. We currently do not expect a material impact on our consolidated financial statements.