Components of the 18.037% Seattle combined top rate on wages

What this dataset measures

Built to test whether Washington's 9.9% millionaires tax would be the highest, or among the highest, state income tax rates, and to show how marginal and average rates differ for the households that pay it.

Geography

United States, Washington, United States

Unit of observation

Jurisdiction; household income level and jurisdiction; tax component

Update cadence

Annually, when the Tax Foundation publishes its state rate table

Curator

FactHub Research Team

Supporting files

Source snapshots, manifests, quality reports, documentation, and other materials used to produce or review this release.

• build_rates.js Transformation manifest · text/javascript · 6 KB (6,098 bytes)

  Node.js script holding every input and computing all tables.

Saved analyses

Sources

1. Tax Foundation Top rates and brackets for 2026

   Retrieved October 21, 2026. Tax Foundation content; facts transcribed. Rates transcribed as facts; not redistributed as a table copy

   Reliability: Advocacy group. Tax Foundation is a nonprofit that favors low, broad-based taxes; its annual state rate table is widely used as a reference. Its 2026 table lists Washington's top capital gains rate as 9%, which the Department of Revenue contradicts (9.9%).

2. Washington State Legislature Washington's 9.9% rate and $1 million household deduction from 2028

   Retrieved October 21, 2026. Public record of the Washington State Legislature. Public record

   Reliability: Government. Nonpartisan final bill report for ESSB 6346 (2026 c 238).

3. Massachusetts Department of Revenue Massachusetts 4% surtax threshold for 2026 ($1,107,750)

   Retrieved October 21, 2026. Public government information. Public record

   Reliability: Government. State revenue department; the surtax threshold is indexed annually under the state constitution.

4. Tax Foundation Components of the 18.037% combined Seattle top rate on wages

   Retrieved October 21, 2026. Tax Foundation content; facts transcribed. Figures transcribed as facts

   Reliability: Advocacy group. January 2026 analysis by a nonprofit that favors low, broad-based taxes; it counts employer-paid payroll taxes as falling on employees.

5. Washington State Department of Revenue Washington capital gains tax rates: 7% plus 2.9% on gains over $1 million

   Retrieved October 21, 2026. Public government information. Public record

   Reliability: Government. The agency that administers the capital gains tax.

Limitations and reproducibility

Reproducible: build_rates.js contains every input rate and bracket and recomputes all tables; inputs are transcribed from the sources listed.

• Statutory top marginal rates only; local income taxes (such as New York City's and Portland-area taxes) and payroll taxes are excluded from the ranking.
• Hawaii's reported increase to 13% from 2027 comes from news reports and was not checked against the statute; Washington's rank is the same whether Hawaii's top rate is 11% or 13%.
• Effective rates assume a married couple filing jointly with wages only and the standard deduction or exemption; real returns have other income, deductions and credits. California's 1.3% SDI payroll tax on wages is not included.
• Some 2026 bracket thresholds in the Tax Foundation table use 2025 inflation widths.
• The Seattle combined rate counts employer-paid payroll taxes as if workers bore them, which is the Tax Foundation's method, not a statement of who legally pays.