Rental Property Investor · Mercer Island, WA · Member since 2008 · 22k+ posts · 14k+ votes
16y
Look at this page on the Clark county assessors office. It says you can call them and discuss your valuation. If you and them still disagree you can file an appeal. You've missed the Jan 15 deadline for this year, so you'll have to do it next year if you can't come to an agreement.
Note that the assessed values and taxes don't go in lock step. Just because values go down does not mean taxes will go down. The tax rate is set based on the total budgeted income needed and the total value of all properties. So, if values fall by 20%, but the budget remains the same, they county may simply raise the tax rate by 20% to make up for the shortfall.