There are four restrictions or limits that affect how high property taxes can go.
The 1% constitutional limit: The primary limitation on property taxes was established by the 55th amendment to the Washington State Constitution in 1972. Article 7, Section 2 of the Constitution and RCW 84.52.050 limit the total regular property tax levy to a maximum of $10.00 per $1,000 of the market value of property. Excluded from this $10 limit are levies for ports and public utility districts.
Statutory maximum rates for districts: State law (RCW 84.52.043) establishes maximum levy rates for the various types of taxing districts (the state, counties, cities and towns, fire districts, and the like). In addition, this statute establishes a maximum aggregate rate of $5.90 per $1,000 of assessed value for counties, cities, fire districts, library districts and certain other junior taxing districts. The state levy for support of common schools is not subject to the $5.90 limit, although it is subject to the constitutional $10 limit.
The 101% limit: In 1971, legislators established a limitation on the increase in regular property taxes for taxing districts. The current limit each year for most districts is 101% of their highest lawful levy since 1985, plus an additional amount to allow for new construction within the district. The 101% limit applies to the total amount of property tax for a taxing district, not to individual properties.
With majority voter approval, districts may raise the 101% limit in order to exercise more levy authority under statutory and constitutional limits.
Detailed information about the 1 percent limits is provided by this State Department of Revenue publication (external link).
Excess levies: Most districts can submit propositions for additional property tax levies to a vote of the people. Local school districts have no regular levy authority (although they are allocated funds from the statewide school levy) so they receive a substantial portion of their funding from voter-approved excess levies. Excess levies must be authorized by a 60% majority of the voters, except for school levies which only require a simple majority, and such levies are not subject to any of the limitations described above.
The Assessor uses the taxing district budget request, the total assessed value of the taxing district and the limitations to set the levy rate. Rates are expressed in dollars per every thousand dollars of assessed value.
The regular levy for each taxing district is reviewed by county authorities for compliance with the 101% limit, the district's statutory rate limit and the $5.90 and 1% limits before the levy is made. If the statutory or 101% limits are exceeded by an individual district, then their levy is reduced to a lawful amount.
The statutes establish a district hierarchy for rate reductions if the aggregate limits are exceeded and rates are reduced accordingly.