The bill introduces an exemption for modifications made to class four residential properties, specifically aimed at increasing living space within existing structures. The exemption allows property owners to benefit from a reduction in property taxes based on the lesser of the increase in market value due to the modification or 15% of the market value from the previous year. However, this exemption is not applicable for modifications made within three years of the property's initial construction, and only one exemption can be granted 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 using existing resources, and the provisions of the new section are intended to be integrated into the existing legal framework of Title 15, chapter 6, part 2. The bill specifies that the exemption will take effect for property tax years beginning after December 31, 2025.