Washington Capital Gains Tax Calculator

Washington does not levy a general individual income tax, but imposes a dedicated 7.00% excise tax strictly on long-term capital gains exceeding the statutory threshold of $278,000, with statutory exemptions for real estate, retirement assets, and qualified family-owned small businesses.

Under Washington statutory law (RCW 82.87), the 7% tax applies exclusively to long-term capital gains allocated to Washington that surpass the annual inflation-adjusted standard deduction ($278,000 for 2026). Real estate transactions, qualified retirement accounts (401k, IRA), agricultural land, and timberland are explicitly exempt by statute.

That matters for high-net-worth individuals, portfolio managers, corporate executives, and real estate investors alike, since state income taxes significantly affect net internal rates of return (IRR) on capital dispositions, 1031 exchange planning, installment sale structuring, and equity compensation exercises (ISOs, NSOs, and RSUs).

Institutional wealth managers and private equity underwriters have to weigh both statutory tax rates and multi-jurisdictional residency rules when running these numbers. Publicly traded securities, privately held business interests, real property, digital assets: whatever is being sold, evaluating the state-level tax exposure is a key part of pre-liquidity tax modeling and post-sale wealth preservation.

Proper capital asset planning in Washington means tracking taxable events across both federal and state reporting cycles. Timing and holding structure drive net after-tax proceeds, so investors need to look closely at how federal adjusted gross income (AGI) baselines interact with state modifications before closing on any substantial transaction.

Washington is not an income tax state and this is not an income tax. It is a standalone excise tax on the sale or exchange of long-term capital assets, sitting alongside a personal income tax that does not exist, which is why your salary is irrelevant to the calculation below and why there are no brackets for the gain to stack into.

The tax reaches only the gain above a standard deduction of $278,000, taxes the next $1,000,000 of that excess at 7%, and taxes anything beyond at 9.9%. Real estate is outside the tax entirely, and so are retirement accounts. The $278,000 figure is the most recent amount published by the Department of Revenue; the deduction is inflation-adjusted, and the DOR had not released a 2026 figure when these tables were verified, so the confirmed prior-year amount is used rather than an estimate.

The calculation in full:

1. Start with the net long-term gain. Losses on other long-term assets are netted against it first.
2. Subtract the standard deduction. The first $278,000 of gain is not taxed. A gain at or below that line produces no Washington tax at all, which is why the calculator returns zero for most sales.
3. Tax the first $1,000,000 of the excess at 7%. This is the base rate written into the tax.
4. Tax anything above that at 9.9%. The second tier applies to taxable gain past $1,000,000, meaning a total gain past $1,278,000.
5. Effective rate. Tax divided by the whole realized gain. Because the deduction comes off the front, the effective rate starts at zero and climbs slowly toward the headline rates; it never reaches 7% exactly.
6. Net proceeds. Subtract the excise tax from the gain. Your other income does not enter this calculation at any point.

Consider an investor in Washington who realizes $378,000 in long-term capital gains from selling appreciated stock during the year.

1. Apply the exemption threshold. Washington's excise tax on long-term capital gains only reaches gains above the statutory standard deduction, set at $278,000 for 2026. The first $278,000 of any investor's long-term gains is entirely untaxed at the state level.
2. Isolate the taxable slice. Subtract the threshold from the total gain (that's $378,000 minus $278,000) and you get $100,000 of taxable long-term gain actually subject to the tax.
3. Apply the 7% rate. $100,000 × 7.00% = $7,000, the Washington capital gains tax due on this sale.
4. Effective rate. Spread across the entire $378,000 gain rather than just the taxable slice, that $7,000 works out to an effective rate of just 1.85% ($7,000 ÷ $378,000).
5. Net proceeds. After paying $7,000 in state excise tax, the investor retains $371,000 of the original $378,000 gain.

At a realized gain of $278,000. The tax is $0.00 and the reported marginal rate is 0.00%. The $278,000 standard deduction under the Washington excise tax removes the entire gain from the base.

At a realized gain of $278,100, one hundred dollars later. The tax is $7.00 and the marginal rate becomes 7.00%. This is a deduction rather than a cliff: crossing it costs seven dollars, not seven percent of the whole gain. That distinction is the single most valuable thing on this page, because the analogous threshold in several state estate taxes is a cliff and behaves in the opposite way.

At a realized gain of $1,278,000. The tax is $70,000.00, the effective rate 5.48%, the marginal rate still 7.00%. That is $278,000 of deduction plus the full $1,000,000 first tier.

At $1,278,100. The tax is $70,009.90 and the marginal rate steps to 9.90%. The 2.9 point surcharge under ESSB 5813 applies to the excess above $1,000,000 of taxable gain only, so the step at the boundary is $9.90 rather than a restatement of the whole bill.

The marginal cost of the next $1,000, in both tiers. Below the second tier, moving from $500,000 to $501,000 of gain moves the tax from $15,540.00 to $15,610.00: $70.00 per $1,000. Above it, moving from $1,500,000 to $1,501,000 moves the tax from $91,978.00 to $92,077.00: $99.00 per $1,000. A seller sitting near $1,278,000 is choosing between those two figures on every additional dollar.

The reverse question. The largest gain that carries no Washington tax at all is $278,000. The largest that stays entirely at 7% is $1,278,000. A seller who can split a $1,556,000 realization across two years keeps both years inside the first tier and pays $70,000.00 twice instead of $70,000.00 plus 9.9% on the excess.

Right method against wrong method, priced. The common error is applying 7% to the whole gain rather than to the gain above the deduction. On a $500,000 realization that gives $35,000 against the $15,540.00 the engine returns, overstating by $19,460.00. The engine only returns $35,000.00 at a gain of $778,000, which is $500,000 of taxable gain plus the deduction. The deduction is not optional and not phased out: it applies at every gain level in the sweep.

• The engine does not test whether the gain qualifies. Real estate, most retirement accounts, livestock and certain family-business sales are outside the Washington excise tax entirely, and none of those exclusions exist in this code path: whatever is entered is treated as taxable long-term gain above the deduction.
• The charitable donation deduction and the qualified family-owned small business deduction are not applied.
• The $278,000 deduction is the confirmed 2025 figure. Washington indexes it, and the Department of Revenue had published no 2026 amount at the time this table was verified, so every threshold on this page is the 2025 one. This calculator handles state statutory modeling with penny-exact precision, but a few federal and transactional complexities are still worth a closer look:
• Federal Capital Gains Taxes: Federal long-term brackets (0%, 15%, 20%) and short-term ordinary rates up to 37% under IRC § 1.
• Net Investment Income Tax (NIIT): The 3.8% surtax on net investment income under IRC § 1411 for single filers over $200,000 (married joint over $250,000).
• Alternative Minimum Tax (AMT): Federal AMT calculations under IRC § 55 impacting incentive stock option (ISO) exercise spread.
• Section 1031 Like-Kind Exchanges: Tax deferral mechanisms for real property held for productive use in trade, business, or investment.
• Qualified Small Business Stock (QSBS): Federal Section 1202 gain exclusions where state conformity varies significantly.

• Assuming Federal Rate Parity: Most states do not offer preferential long-term capital gains rates; gains are taxed at standard ordinary income rates.
• Failing to Track Holding Periods: Short-term gains (assets held ≤1 year) generate higher federal tax liabilities even if state rates treat both holding periods identically.
• Underestimating Multi-State Apportionment: Selling real estate or business assets located in other jurisdictions triggers multi-state non-resident return filing obligations.
• Neglecting Underpayment Penalties: Substantial one-time liquidity events require prompt estimated tax payments within the quarter of sale to avoid statutory penalties.
• Mismatched Cost Basis Records: Failure to document reinvested dividends, stock splits, or structural return-of-capital distributions leads to inflated taxable gain calculations.

• Washington State Department of Revenue: 2026 Statutory Individual Income Tax Rate Schedules. dor.wa.gov
• Internal Revenue Service (IRS): Publication 544 (Sales and Other Dispositions of Assets) and Publication 550 (Investment Income and Expenses). irs.gov/publications/p544