Washington Residency Rules 2026: No Income Tax, 9.9% Capital Gains

Who needs to read this

Washington has no personal income tax: no tax on wages, and no state income tax return. For most movers the game is entirely about establishing Washington residency and defending it against the state you left. But Washington is not a zero-tax state, and two of its taxes have residency rules of their own:

• You're moving to Washington from California, Oregon, or another income-tax state
• You hold appreciated stock or a business stake and a sale or IPO is on the horizon; Washington's capital-gains excise now reaches 9.9% at the top
• You split time between Washington and an income-tax state
• Your estate may exceed $3 million; Washington's estate tax has no income-tax escape hatch
• You left Washington with large unsold gains and assume the state is done with you

How Washington defines residency

For income tax, there's nothing to define: the tax doesn't exist. Residency matters in two places:

The capital-gains excise. Washington taxes long-term capital gains of residents (for intangibles like stock) at 7%, plus 2.9% on gains over $1 million. Under RCW 82.87.020, you are a resident for a taxable year if either:

1. You were domiciled in Washington during the year, unless you maintained no permanent place of abode in Washington all year, maintained one elsewhere all year, and spent no more than 30 days in the state; or
2. You were not domiciled in Washington but maintained a place of abode and were physically present for more than 183 days during the year.

So Washington uses the classic two-part structure (domicile plus a statutory 183-day test), just pointed at a narrower tax.

The estate tax. It applies to decedents domiciled in Washington (worldwide assets) and to nonresidents' Washington real estate and tangible property.

Your former state's rules are the third, and usually biggest, piece: California, Oregon, and the rest decide for themselves whether you really left.

Counting the days

For the capital-gains excise, any portion of a calendar day in Washington counts as a day, and both thresholds aggregate across the year:

• A "day" is "a calendar day or any portion of a calendar day"; an evening arrival counts.
• The 30-day ceiling (for domiciliaries claiming out-of-state status) and the 183-day statutory-resident test both aggregate across the year.
• The same day log serves double duty: it proves your Washington presence for Washington purposes and your absence for your former state's audit. Movers from day-counting states like New York or Minnesota should track from day one; iReside-style contemporaneous records beat reconstructed calendars in every audit.

Domicile: the stickier test

Domicile, your true permanent home, decides both the capital-gains excise's reach and the estate tax, and it's the exact battleground your former state will choose. Gains on intangible property are allocated to Washington if you were domiciled in Washington at the time of the sale (RCW 82.87.100); your former state will argue the mirror image. What makes a Washington domicile stick:

• A real Washington home: owned or leased, actually lived in, comparable to what you left
• Family moved with you; children in Washington schools
• Washington driver's license, vehicle and voter registration
• Physicians, advisors, banking relocated
• The majority of your days actually spent in Washington
• The old state's home sold or leased out, not held empty

Washington itself rarely has to litigate domicile into the state; the fights are almost always with the state you left, on its factors and its timeline.

Part-year residents and nonresidents

There is no part-year income tax return because there is no income tax. What actually applies:

• Capital-gains excise: if you meet the resident definition and your long-term gains exceed the standard deduction ($278,000 for 2025, inflation-adjusted), you file a capital gains return with DOR, due at the federal income-tax deadline, filed and paid electronically. Exempt categories include real estate, interests in privately held entities to the extent attributable to real estate, retirement-account assets, depreciable business assets, and certain timber, livestock, and commercial-fishing interests. A credit is allowed for legally imposed taxes paid to other jurisdictions on the same gains.
• Tangible property gains are allocated to Washington if the property was in the state at the time of sale, and can follow you even after moving away if it was in Washington the year before the sale and no other state taxes the gain.
• Your former state's part-year return (California 540NR, Oregon Form OR-40-P, etc.) is where the move year actually gets reported.

Changing your residency status

The checklist is aimed at the state you're leaving:

• Move first, sell later. For stock and other intangibles, domicile at the moment of sale controls: a move completed and seasoned before a liquidity event is defensible; one dated a month before closing is a target
• Establish the Washington home and spend most of your days there
• Flip the paper trail in one sweep: license, registrations, voter rolls, mailing addresses, advisors
• Sever the old abode: an empty house kept "just in case" is the classic audit loss
• File the former state's final part-year return with a clean departure date
• Keep the day log through the move year and at least the next full year

Remember Washington's own 30-day rule cuts the other way for leavers: a Washington domiciliary who keeps no abode in the state, keeps one elsewhere, and stays under 30 Washington days escapes resident status for the capital-gains excise.

How Washington enforces its rules

Washington's own enforcement is data-driven but narrow; the bigger risk for most movers is the former state's residency audit:

• The Department of Revenue administers the capital-gains excise through federal data matching: the return piggybacks on your federal filing, and unreported large gains by apparent Washington residents are easy to spot
• Estate tax enforcement runs through the probate process; returns and payment are due nine months after death, with interest accruing daily
• Late filing and payment penalties apply to the capital-gains excise; paying at least 80% of the tax by the original deadline avoids the late-payment penalty
• The heavier enforcement risk for most movers is the former state's residency audit: California's FTB and Oregon's DOR both work Washington moves hard, using the usual toolkit of license records, cell data, and credit-card trails

Common mistakes

• Treating "no income tax" as "no taxes." The 7%–9.9% capital-gains excise, a 10%–35% estate tax band, and B&O tax on business receipts all still apply.
• Moving weeks before a stock sale. Domicile at the time of sale controls the allocation, and your former state gets a vote. Unseasoned moves lose.
• Forgetting Washington taxes the gain too. Escaping California's 13.3% into Washington's 9.9% tier is a smaller win than the brochure promised.
• Assuming the estate tax mirrors federal. The exclusion is about $3 million (a Seattle house plus a retirement account can clear it) and there's no income-tax offset for heirs.
• Keeping the old home available. It's the single strongest fact your former state can cite against your move.
• No day records. Both Washington's 30-day and 183-day tests and your former state's audit turn on days you'll need to prove.