State tax docs / States / Washington
Washington state income tax: engine rules, 2026
How the QuantCalc engine computes Washington tax for tax year 2026, rule by rule, with the official source for each rule. Verification status: No income tax (what this means).
On this page: How the tax is computed · No broad income tax · Capital gains · Worked examples · After 2026 · Not calculated ·
Verification. Machine-readable: this state's entry in the
engine config and the provenance file
(key WA).
How the tax is computed
Every step the engine takes for Washington, in the order it takes them. Steps marked with a filing status or household type apply only there. Each step links the section below that carries Washington's figures and the official sources for it; the calculation order page describes every step for all jurisdictions.
- No broad income tax A jurisdiction with no brackets returns 0 at once, except Washington's capital-gains excise below. Military pay is still attributed per person in the detail record.
Washington's values · engine step (compute_state_tax_detail). Sources (No broad income tax): Income tax (checked 2026-10-12); Income tax (checked 2026-10-12) - Washington capital-gains excise The excise rate on long-term gain above the excise deduction, plus the additional rate on gain above the high threshold. Nothing else is taxed.
Washington's values · engine step (compute_state_tax_detail). Sources (Capital gains): RCW 82.87.040 Tax imposed (checked 2026-10-12); RCW 82.87.060 Deductions (checked 2026-10-12); Capital gains tax (checked 2026-10-12); Frequently asked questions about Washington's capital gains tax (checked 2026-10-12); SB 5813 - 2025-26 (bill summary) (checked 2026-10-12); Income tax (checked 2026-10-12)
No broad income tax
Washington levies no broad personal income tax: wages, pensions, IRA distributions, Social Security and Roth conversions are not taxed by the state.
- Income tax, Washington Department of Revenue. Washington levies no individual income tax for tax year 2026, so wages, Social Security, pensions and IRA distributions carry no Washington income tax; a 9.9% tax on income over $1 million enacted by SB 6346 (2026) starts only on Jan. 1, 2028. Checked 2026-10-12.
- Income tax, Washington Department of Revenue. Washington levies no broad personal income tax. Checked 2026-10-12.
Capital gains
- No income tax, but an excise of 7% applies to long-term gain above $278,000, plus 2.9% on taxable gain above $1,000,000.
Source review notes (what the sources do not state outright, or what the engine does not carry):
- The 2026 inflation-adjusted standard deduction is not yet published by WA DOR; the engine carries the 2025 $278,000 as a proxy.
- RCW 82.87.040 Tax imposed, Washington State Legislature. Washington imposes a 7% excise on an individual's Washington capital gains, plus an additional 2.9% on the portion above $1,000,000 from January 1, 2025 (9.9% combined). Checked 2026-10-12.
- RCW 82.87.060 Deductions, Washington State Legislature. Gains are reduced by a standard deduction of $250,000 (inflation-adjusted under RCW 82.87.150) that is one combined deduction for spouses or domestic partners, whether they file jointly or separately. Checked 2026-10-12.
- Capital gains tax, Washington Department of Revenue. The inflation-adjusted standard deduction is $278,000 for 2025, which the engine uses for 2026 until the 2026 figure is published; real estate and assets held in retirement accounts are exempt from the excise. Checked 2026-10-12.
- Frequently asked questions about Washington's capital gains tax, Washington Department of Revenue. Transactions inside 401(k)s, IRAs, Roth IRAs and similar retirement accounts are outside the capital gains excise, so only taxable brokerage gains are subject to it. Checked 2026-10-12.
- SB 5813 - 2025-26 (bill summary), Washington State Legislature. ESSB 5813 was enacted as Chapter 421, Laws of 2025, adding the 2.9% tier on gains above $1,000,000. Checked 2026-10-12.
- Income tax, Washington Department of Revenue. Washington Department of Revenue: "Washington does not currently have an individual income tax" (and 1 more quoted passage) Checked 2026-10-12.
Worked examples
Computed by the engine for the fixed households below (the same ones for every state, so states compare directly). Federal tax is not supplied, so a federal-tax deduction is not taken; the income tests use the sum of the components as income.
| Household (engine inputs) | State tax |
|---|---|
| Single, 67: $30,000 private pension, $20,000 IRA, $10,000 interest, $24,000 Social Security ($17,000 federally taxable), $5,000 long-term gain | $0 |
| Married filing jointly, 70: $40,000 public pension, $40,000 IRA, $20,000 interest, $40,000 Social Security ($34,000 federally taxable), $10,000 long-term gain | $0 |
| Single, 60: $60,000 other ordinary income and a $50,000 Roth conversion | $0 |
| Married filing jointly, 66: $30,000 IRA, a $40,000 Roth conversion, $30,000 Social Security ($25,500 federally taxable) | $0 |
| Single, 58: $36,000 military retirement pay and $30,000 wages | $0 |
| Married filing jointly, ages 67 and 61: $50,000 IRA, $10,000 interest, $30,000 Social Security ($25,500 federally taxable), each spouse's age given | $0 |
Line by line
The intermediate lines the engine records while it computes each example (its detail record, printed as it comes out; lines that are zero are left out). The engine's documentation build checks that the lines add up to the taxable income and the tax, for every state, filing status and a grid of households. Each line links the engine step that produces it.
Single, 67: $30,000 private pension, $20,000 IRA, $10,000 interest, $24,000 Social Security ($17,000 federally taxable), $5,000 long-term gain: $0
| Line | Amount |
|---|---|
| = State taxable income | $0 |
| Tax from the rate schedule | $0 |
| = Tax | $0 |
Married filing jointly, 70: $40,000 public pension, $40,000 IRA, $20,000 interest, $40,000 Social Security ($34,000 federally taxable), $10,000 long-term gain: $0
| Line | Amount |
|---|---|
| = State taxable income | $0 |
| Tax from the rate schedule | $0 |
| = Tax | $0 |
Single, 60: $60,000 other ordinary income and a $50,000 Roth conversion: $0
| Line | Amount |
|---|---|
| = State taxable income | $0 |
| Tax from the rate schedule | $0 |
| = Tax | $0 |
Married filing jointly, 66: $30,000 IRA, a $40,000 Roth conversion, $30,000 Social Security ($25,500 federally taxable): $0
| Line | Amount |
|---|---|
| = State taxable income | $0 |
| Tax from the rate schedule | $0 |
| = Tax | $0 |
Single, 58: $36,000 military retirement pay and $30,000 wages: $0
| Line | Amount |
|---|---|
| = State taxable income | $0 |
| Tax from the rate schedule | $0 |
| = Tax | $0 |
Married filing jointly, ages 67 and 61: $50,000 IRA, $10,000 interest, $30,000 Social Security ($25,500 federally taxable), each spouse's age given: $0
| Line | Amount |
|---|---|
| = State taxable income | $0 |
| Tax from the rate schedule | $0 |
| = Tax | $0 |
After 2026: how the amounts move
A request with projection (API) estimates a later tax year from these rules: every
dollar amount and age test below moves the way Washington's law moves it. Rates and the rules themselves stay the 2026 ones
(how projection works).
| Amounts (engine fields) | After 2026 | What the law says, and the source |
|---|---|---|
cg_excise_deduction | Indexed: CPI-U, all items, Seattle area (BLS): latest CPI available October 1 over the prior 12-month period; the increase rounded to the nearest $1,000. The engine carries the 2025 figure (the latest published) for 2026, so a projection adds 1 year of indexing at the factor's average annual rate. | RCW 82.87.150: each October the department multiplies the standard deduction (an 'applicable amount') by one plus the change in the Seattle-area CPI-U over the prior 12 months, rounding to the nearest $1,000, never downward; the result applies the following calendar year. The engine carries the 2025 amount ($278,000).
|
cg_excise_high_threshold | Fixed in law: held at the rules-year amount in every later year. | RCW 82.87.040(1)(b): the additional 2.9% applies to Washington capital gains above $1,000,000; this amount is not among the 'applicable amounts' RCW 82.87.150 indexes, so it is fixed.
|
Enacted for later years, not applied by the projection
None found: the research found no change enacted for years after 2026 beyond the schedules above.
What the engine does not calculate, and known approximations
- The excise standard deduction is the 2025 amount ($278,000), used for 2026 until the 2026 amount is published.
- Only brokerage long-term gains are entered; the excise's exemptions for retirement-account and real-estate gains are outside the inputs.
- Married filing separately: Washington gives spouses one combined capital-gains standard deduction whether they file jointly or separately; the engine gives the separate filer the whole deduction, which is right only when the other spouse has no Washington capital gains. Sources: RCW 82.87.040 Tax imposed (checked 2026-10-12); RCW 82.87.060 Deductions (checked 2026-10-12); Capital gains tax (checked 2026-10-12); Frequently asked questions about Washington's capital gains tax (checked 2026-10-12); SB 5813 - 2025-26 (bill summary) (checked 2026-10-12); Income tax (checked 2026-10-12).
- The capital-gains excise's charitable donation deduction (RCW 82.87.080) needs the donations and is not calculated. Sources: RCW 82.87.040 Tax imposed (checked 2026-10-12); RCW 82.87.060 Deductions (checked 2026-10-12); Capital gains tax (checked 2026-10-12); Frequently asked questions about Washington's capital gains tax (checked 2026-10-12); SB 5813 - 2025-26 (bill summary) (checked 2026-10-12); Income tax (checked 2026-10-12).
What the engine does not calculate for any state (itemized deductions, credits beyond those listed, part-year residents, and more) is listed on the calculation order page.
Verification
No income tax No income tax. The capital-gains excise (RCW 82.87) is pinned by an exact unit test.
- Golden scenarios (hand-computed expected tax, asserted to within $1): none for this state.
- State-specific unit tests:
test_wa_cg_excise,test_legacy_request_equals_v2,test_refusals. - Structural tests covering every state: 2.