Revise ABLE Act definitions to conform to Montana individual income tax code

House Bill 671 revises the Montana Achieving a Better Life Experience (ABLE) Act to align its definition of the "Internal Revenue Code" with the definition used in the Montana individual income tax code. This change ensures consistent interpretation of federal tax law references for individuals participating in or establishing Montana ABLE accounts. By linking the ABLE Act's definition to the state income tax code, the bill aims to standardize how these financial accounts are treated under state law. The bill took effect immediately upon passage and applies retroactively to income tax years beginning after December 31, 2024.