Supplementary assessments provide equity amongst property owners by capturing the increased value of properties that were only partially completed on December 31, of the year prior to the current tax year, and have since become completed or occupied. The value gained is applied on a prorated basis and applies only when new construction is completed, occupied, or when a project begins its operational function during the current tax year.
When new construction is completed or becomes occupied, the owners receive municipal services and the supplementary assessment contributes towards equitable distribution of the costs to provide those services.
An example scenario: the annual assessment for a 60% completed home on December 31 is $100,000 and an assessor inspects on May 15th, determines the home is lived in or completed, and its completed value is $160,000. Then the homeowner will receive a supplementary assessment for $60,000 from June 1 to Dec 31 of the current tax year where the owner would be responsible for a prorated assessment of $35,000 [($60k/12) * (7 months) = $35,000] and would pay taxes on that assessment amount.