Here is a good video about King County, Washington that describes why your property taxes may increase, but the value of your home was assessed for less than last year. King County is a Revenue-based property tax system.
“Washington State operates under a “revenue-based” property tax system in which taxing districts, such as fire, library and school districts, submit their annual adopted budgets to the County Assessor who has the responsibility to set the levy rate that is necessary to meet the adopted budgets regardless of assessed values. We are one of the states that operates under the “revenue-based” system.
King County has 700,000 + properties, 163 taxing districts, and 594 tax levy codes. A property located in one tax code has a number of separate taxing districts (fire, library, schools, etc). As property values decrease, there is a natural assumption that property taxes will also decrease – that might not be the case for thousands of King County property owners.”