King County, WA Car Tax & Registration (2026)
In King County (Seattle), a car purchase is taxed at about 10.55% combined (plus a 0.3% motor-vehicle add-on). And the big one: if your address is inside the Sound Transit district (parts of King County), you also owe the annual RTA excise tax — 1.1% of your car's depreciated value, which can be hundreds of dollars a year. Washington has no emissions test.
Verified July 2026 from official sources. How we verify fees.
What you'll pay in King County
- Combined sales tax: 10.55% (+ 0.3% motor-vehicle add-on on purchases)
- RTA / Sound Transit tax: 1.1% of value/year (part of county)
- Base tab fee: ~$43 + weight fee · Title: $15 · Local TBD fee: $20–$50
- Emissions test: Not required (ended 2020)
The RTA tax is the thing to check
The Sound Transit boundary cuts through King County by address — two neighbors can pay very different amounts. Because the RTA tax is 1.1% of your vehicle's depreciated MSRP every year, a newer car can add several hundred dollars annually. Verify your exact address against Sound Transit's boundary tool before you budget. Estimate the purchase cost on our Washington title & tax page.
Frequently asked questions
Does King County have the RTA / Sound Transit tax?
Partly — the Sound Transit district covers parts of King County. If your home address is inside it, you owe 1.1% of your car's depreciated value every year at renewal. Check your exact address on Sound Transit's boundary map.
What is the car sales tax in King County, WA?
About 10.55% combined around Seattle, plus a 0.3% motor-vehicle add-on on a purchase.
Does King County require an emissions test?
No — Washington ended emissions testing statewide on January 1, 2020.