Understanding the MID Assessment Formula

The MID’s assessment formula was updated as part of the 2013 renewal process in an effort to create more transparency and predictability while maintaining previous efforts to ensure different property types are assessed fairly. In addition to a base formula, several “ceilings” come into effect for specific property types. An inflationary factor is applied to most years of the assessments, while property values are updated twice during the ten years using the King County Tax Assessor data. The cumulative inflation factor is calculated by multiplying the annual CPI by all the previous annual CPIs since 2013. 

Annual MID assessments are calculated from a formula prescribed in the MID’s authorizing ordinance that was adopted in May 2013.

The following also provides a detailed explanation of the Assessment timeline, formula rationale and ceilings.

Seattle-Tacoma-Bremerton CPI-U and Cumulative CPI-U for Assessment

Assessment Year CPI-U% Cumulative CPI-U Factor
2013 Not Applicable 1
2014 1.3% 1.013
2015 1.84% 1.0316
2016 1.36% 1.0457
2017 2.21% 1.0688
2018 3.00% 1.1008
2019 3.00% 1.1330
2020 2.54% 1.1627

If Seattle-Tacoma-Bremerton CPI-U is more than 3% for a specific assessment year, then 3% is used to calculate the cumulative CPI-U Factor for calculation for that year.


Assessment Formula & Rationale

Formula Rationale Rate Notes
Assessment / $1,000 TAV Reflects differential benefit associated with different land uses, investment value of property within land uses, and economic activity. $0.3 $0.37 Total Budget set to 2% over 2012; Ratio set to 45% Value to 55% Land Area
Assessment / Land Sq. Ft. Reflects common level of services to all benefitting properties. $0.32 Total Budget set to 2% over 2012; Ratio set to 45% Value to 55% Land Area. Multiply by Cumulative CPI-U Factor.

Ceiling Rationale & Factor Calculation

Ceillings Rationale Factor Calculation
TAV Ceiling Assures that properties are not unfairly assessed compared to benefits received. $1.84 per $1,000 total appraised value Cumulative CPI-U Factor * Factor * King County total appraised value / $1000
Building Square Footage Ceiling Limits assessments on small buildings due to limited rent-producing potential. $0.17 per building net square feet If FAR > 0.5, then Cumulative CPI-U Factor * Factor * Building new square feet
Hotel Room Ceiling Limits assessments on hotels. Value received relates to per room occupancy and revenue potential. $80.00 per room Cumulative CPI-U Factor * Factor * Number of rooms
Residential Unit Ceiling Limits assessments on residential units. Value received relates to per unit occupancy. $125.00 per unit Cumulative CPI-U Factor * Factor * Number of units
Surface Parking TAV Ceiling Limits assessments on surface parking to compensate for limited benefits. $0.70 per $1,000 total appraised value Factor * King County total appraised value / $1000
Nonprofit Reduced Rate Limits assessments on properties owned by nonprofits and occupied by charitable uses. Reduced rate requires application and documentation process. 25% of basic formula Factor applied to occupied % of occupied use for charitable purposes