Quick answer: Washington's 7% capital gains excise tax does not apply to a house sale — real estate is specifically exempt. What does apply is the Real Estate Excise Tax (REET), a transfer tax on the price, not the gain. See the full cost picture in the Washington probate real estate sale calculator.
Real estate is exempt, in plain terms from the state itself
What actually applies instead: REET
Rather than a tax on the gain, Washington charges the Real Estate Excise Tax on the sale price itself — graduated by price tier, generally paid by the seller. It applies regardless of whether the sale produced any gain at all, which is a fundamentally different mechanism than every capital-gains-on-the-profit model used elsewhere.
The federal side is unaffected either way
None of this changes the federal picture. Under IRC § 1014, the house's basis still steps up to fair market value on the date of death, so federal tax applies only to appreciation after that date — Washington simply never takes a state-level cut of that gain, unlike most other states in this cluster.
Not an income tax, and not the same as the state estate tax
The capital gains excise tax is legally distinct from an income tax (which Washington's constitution prohibits) and from Washington's separate state estate tax, which applies to larger estates above their own exemption threshold rather than to any one sale transaction.
A local probate attorney can review your estate — many offer a free consultation.
This exemption and REET's structure apply identically whether the sale closes in King, Pierce, Snohomish, or Spokane County — REET does allow some local additions on top of the state portion, which is the one place county matters.