FIN 48, or Financial Accounting Standards Board Interpretation No. 48, provides guidance on how to account for uncertainty in income taxes. It requires companies to recognize and measure tax positions based on a two-step process: first, determining whether a tax position is more likely than not to be sustained upon examination, and second, measuring the amount of tax benefit to recognize based on the likelihood of its realization. This standard aims to enhance transparency and consistency in financial reporting regarding uncertain tax positions.