House Bill No. introduced by J. Gillette proposes an exemption for certain modifications to class four residential properties in Montana. The bill allows for an exemption when modifications are made to add living space to an existing residential structure, which can include increasing the finished area or altering the structure. The exemption is defined as the lesser of the increase in market value due to the modification or 15% of the market value from the previous year. However, the bill stipulates that no exemption will be granted for modifications made within three years of the construction of a new class four residential property, and only one exemption can be claimed within a six-year period. Additionally, the exemption will terminate upon the sale of the property.

The Department of Revenue is tasked with administering this exemption within existing resources, and the provisions of the bill are intended to be codified as part of Title 15, chapter 6, part 2 of the Montana Code. The applicability of this act is set for property tax years beginning after December 31, 2025.