2026 Property Tax Due Dates
April 30
First half
October 31
Second half
Payment Methods
Online, Mail, In-Person
Cowlitz County Treasurer
Phone
(360) 577-3060Office Hours
How to Pay
Online
Pay using credit card or e-check
By Mail
Mail check payable to Cowlitz County Treasurer
In Person
Visit the Treasurer's office — 207 N. 4th Ave., Room 202, Kelso WA 98626, Mon-Fri 8am - 5pm
About Property Taxes in Washington
Washington State property taxes are administered at the county level. Property is assessed at 100% of its true and fair market value as of January 1. Washington levies both a state property tax (used for schools) and local taxes (county, city, school district, fire district, and others). The combined rates vary significantly by county. Washington's property tax system has strong protections for seniors and low-income homeowners, including an exemption that reduces or eliminates taxes for qualifying households regardless of property value.
Payment & Assessment
Washington property taxes are paid in two equal installments: First half: Due April 30 Second half: Due October 31 If the total tax is under $50, the full amount is due April 30. An interest charge of 12% per year applies to late payments, plus a 3% penalty on the first half and 8% on the second half if unpaid. Most counties offer online payment through the county treasurer's website. Contact your county for payment options.
Statewide framework for Washington. Your county's specific rates and deadlines are shown above.
Other Counties in Washington
About Cowlitz County
Cowlitz County is a county located in the U.S. state of Washington. As of the 2020 census, its population was 110,730. The county seat is Kelso, and its largest city is Longview. The county was formed in April 1854. Its name derives from the anglicized version of the Cowlitz Indian term Cow-e-liske, meaning either 'river of shifting sands' or 'capturing the medicine spirit.' Cowlitz comprises the Longview, WA Metropolitan statistical area, which is also included in the Portland-Vancouver-Salem, OR-WA Combined statistical area.
Source: Wikipedia — content available under CC BY-SA 4.0
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Due dates shown are for reference only. Contact your county treasurer's office to confirm official deadlines before making payments.