Illustrative back-cast: a 9.9% tax on Washington income over $1M, 1997-2023

What this dataset measures

ESSB 6346 taxes household income above $1 million. The IRS state tables are the only official, long-run record of how much income Washington's $1M+ filers report and what kind. DOR and ERFC revenue tables give the comparison with the taxes Washington already relies on.

Geography

Washington, United States

Unit of observation

Tax year and geography (IRS); state fiscal year (revenue)

Update cadence

Annual, when IRS releases a new year of state data

Curator

FactHub Research Team

Supporting files

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

• volatility.js Transformation manifest · text/javascript · 8.3 KB (8,496 bytes)

  Node.js script that computes the back-cast, crash scenarios and volatility statistics from the two curated tables. Run: node volatility.js in a folder holding both CSVs.

• build_datasets.js Transformation manifest · text/javascript · 49.4 KB (50,561 bytes)

  Node.js script holding every typed input value and computing the CSV tables and saved analyses for this dataset. Run: node build_datasets.js.

• dataset-parts-irs.json Documentation · application/json · 40.9 KB (41,911 bytes)

  The dataset's limitations, sources, tables, events, saved analyses and forecasts as JSON, as stored in this version.

Saved analyses

Sources

1. IRS Statistics of Income, Historic Table 2: Individual income and tax data by state and size of adjusted gross income (Washington files, 1997-2023) Washington returns, AGI, wages, net capital gain, partnership/S-corporation and business income by AGI class; the $1M-or-more class for 1997-2001 and 2010-2023, $200,000-or-more for 2002-2009. Each row's file is in the sourceFile column.

   Retrieved October 21, 2026. Public domain (U.S. government work). Public domain; values restated, files linked.

   Reliability: Government. Compiled by the IRS from individual income tax returns. The 1997-2001 state files are unedited counts of returns processed in each calendar year; later files are tax-year tabulations with counts rounded to the nearest 10 from 2015.

2. IRS Statistics of Income, Table 1.4: All returns, sources of income, by size of adjusted gross income (U.S., 1998-2023) U.S. returns, AGI, wages, net capital gain and pass-through income for AGI of $1M or more, used to show the 2002-2009 years for which no Washington $1M class exists.

   Retrieved October 21, 2026. Public domain (U.S. government work). Public domain; values restated, files linked.

   Reliability: Government. National sample-based estimates from the IRS individual complete report. Net capital gain and pass-through are FactHub sums of the gain and loss columns, matching the Historic Table 2 U.S. totals within about 1% in 2010-2023.

3. Washington Department of Revenue, Tax Statistics, Table 3: Washington State General Fund Revenues (fiscal years 1998-2024) Retail sales, business and occupation and state property tax revenue to the general fund by fiscal year (GAAP basis, from the state's annual financial report). Each year's file is in the source column.

   Retrieved October 21, 2026. Public record of a Washington state agency. Figures restated with attribution; files linked.

   Reliability: Government. DOR's annual statistical report restating general fund revenue from the state's audited financial statements. FY2002 and FY2025 come from ERFC cash tables because DOR's tables for those years were not available.

4. Washington Economic and Revenue Forecast Council, Revenue Review, September 25, 2026 Total general fund-state collections by fiscal year, FY2005-FY2025 (current definition, cash), and the September 2026 forecast of the individual income tax used as a baseline in the crash scenarios.

   Retrieved October 21, 2026. Public record of a Washington state agency. Figures restated with attribution; the PDF is linked, not hosted.

   Reliability: Government. ERFC is the state's official, bipartisan revenue forecasting body. Its forecast is the basis for the budget; it published no separate risk analysis of the new income tax.

5. Washington Economic and Revenue Forecast Council, Economic and Revenue Forecast, June 2010 (Table 3.15) Total general fund-state collections (GF-S plus related fund, cash) for fiscal years 1998-2004.

   Retrieved October 21, 2026. Public record of a Washington state agency. Figures restated with attribution; archived copy linked.

   Reliability: Government. ERFC historical table under the definition used in 2010; it differs from the current definition, so FY1998-2004 totals are not spliced to FY2005 onward for year-over-year change.

6. OFM Fiscal Note Package 77653, ESSB 6346 (2026), tax on income over $1 million The Department of Revenue's estimate of the income tax (FY2030 $3.732B gross), used as the second baseline in the crash scenarios.

   Retrieved October 21, 2026. Public record of a Washington state agency. Figures restated with attribution; the PDF is linked, not hosted.

   Reliability: Government. Official fiscal note for the enacted bill. It is a static estimate: it states that affected taxpayers do not reduce taxable income.

Limitations and reproducibility

Reproducible: The curated tables hold values read from IRS, DOR and ERFC files named in each row. volatility.js recomputes the back-cast, crash scenarios and volatility statistics; build_datasets.js assembles the saved analyses.

• IRS publishes no Washington $1M+ class for 2002-2009; those rows give the $200,000-or-more class, and U.S. $1M+ data stands in for the shape of the 2001-02 and 2007-09 downturns.
• The 1997-2001 Washington IRS files are a different product (returns processed in a calendar year, unedited) from the 2010+ tax-year tables.
• Returns are not households, and the $1M class is in nominal dollars.
• The back-cast and crash scenarios are FactHub illustrations, not forecasts, and ignore behavioral responses, compliance and the law's capital-gains credit except as noted.
• Revenue by source mixes DOR GAAP figures with ERFC cash figures for two years, and total general fund revenue changes ERFC definition at FY2005.