Relating to: adopting changes to the federal Internal Revenue Code for state tax purposes and modifying administrative rules related to such changes. (FE)

SB 859 updates Wisconsin's state tax code to align with specific federal tax changes. For taxable years starting after December 31, 2025, Wisconsin will use the federal Internal Revenue Code as amended through December 31, 2025, instead of current federal rules. The bill explicitly excludes certain federal tax provisions (like specific sections from recent laws) from Wisconsin's tax calculations and creates new rules to handle differences between state and federal tax treatments. This directly affects Wisconsin taxpayers and businesses by changing how state income tax is calculated based on updated federal rules.