Washington Estate Tax Guide
Last updated: 24 Oct 2025 • Author: Alexander Foelsche CPA (US), WP (DE), RE (CH)
Washington Estate Tax — Overview
Washington imposes a stand-alone Estate & Transfer Tax under RCW 83.100, administered by the Department of Revenue. Speak to a Washington Estate Tax Specialist
Returns are generally due 9 months after death; extensions to file (via My DOR) do not extend time to pay. Nonresident estates are taxed through an apportionment fraction that limits liability to Washington-situs property. RCW 83.100 • WAC 458-57
Key facts
Who must file
- Residents: File when the Washington gross estate meets the filing threshold and/or WA tax is due.
- Nonresidents: File if Washington-situs real or tangible property produces WA tax after apportionment.
- Signer: Personal representative (or person in possession/control if none appointed).
Deadlines
- Return & payment: Due in 9 months.
- Extension to file: Typically up to 6 months via My DOR; does not extend time to pay.
- Interest: Accrues after the original due date until paid.
Computation
- Start with a federal-style base (706 schedules) then apply WA exclusion and brackets.
- Apportionment: Multiply pre-apportioned tax by (WA-situs gross estate ÷ worldwide gross estate).
- Special deductions: QFOBI & Farm (eligibility/documentation required).
Residents vs. nonresidents — situs & apportionment
| Category | What’s included | Notes |
|---|---|---|
| Residents | Worldwide assets; numerator generally includes intangibles. Out-of-state real/tangibles reduce the numerator effect when modeling exposure. | State QTIP and credit-shelter planning can shape the taxable base at each death. |
| Nonresidents | WA-situs real and tangible property in the numerator; most intangibles excluded unless tied to a WA business situs. | Report the fraction on Addendum #4; retain deeds, titles, appraisals, and location evidence. |
Core forms & where to file
Washington DOR
- Washington State Estate & Transfer Tax Return (fillable PDF / Excel).
- Application for Extension of Time to File (via My DOR preferred).
- Addendum #4 — Apportionment for Out-of-State Property.
- Upload template/instructions for e-submission.
Typical attachments
- Federal Form 706 (or 706-NA) pages/schedules; Forms 712 (life insurance).
- Appraisals, deeds/titles for WA property; will/trust; letters of authority.
- Proof of deductible expenses and any claimed QFOBI/Farm eligibility.
Planning highlights
Married couples
- No state portability: consider a state-sized credit-shelter trust.
- Use state QTIP to defer WA tax where appropriate; keep election statements.
Business & farm
- Screen for QFOBI and Farm deductions early; strict tests and documentation.
- Coordinate valuation and continuity requirements before restructuring.
FAQs
Does Washington have portability like the federal DSUE?
No. Unused state exclusion does not transfer to the survivor; plan to capture it at the first death.
How does apportionment work for nonresidents?
Compute a pre-apportioned tax, then multiply by WA-situs ÷ worldwide gross estate. Most nonresident intangibles are excluded from the numerator.
References
- RCW 83.100 — Washington Estate & Transfer Tax (scope, exclusion, deductions, apportionment).
- WAC 458-57 — Rules (definitions, apportionment mechanics, valuation examples).
- Washington Department of Revenue — Estate Tax Return, Addendum #4, My DOR filing/extension guidance.
- IRS Form 706 & Instructions — federal schedules used as documentation scaffolding.