A midyear move requires separate calculations for Washington residency, income source, and the standard deduction. Under the enacted income tax beginning in 2028, the deduction is adjusted by an income ratio—not simply the fraction of the year you lived here.
The examples below illustrate that distinction. They assume Washington residency actually ends and later income has no Washington source. A change of address or payment date alone does not establish either assumption. For the broader framework, see the relocation guide.
Determine the resident and nonresident portions
Under RCW 82A.04.450, enacted as §406 of ESSB 6346, a part-year resident generally includes all adjusted gross income from the resident portion and Washington-source income from the nonresident portion, subject to the statute’s other modifications.
Pass-through items have a separate rule. The resident component uses the item’s total amount multiplied by resident days divided by days in the entity’s tax year. The nonresident component uses the Washington-source amount multiplied by the corresponding nonresident-day ratio. Do not allocate every item solely by when cash was distributed.
Adjust the deduction by income
RCW 82A.04.363, enacted as §315, adjusts the standard deduction for taxpayers who are not residents for the entire year. Multiply the applicable deduction by Washington base income divided by federal adjusted gross income from all sources, with the fraction capped at one.
For 2028, the starting deduction is $1 million, shared by spouses and state-registered domestic partners regardless of filing status. These simplified examples assume $4 million of federal AGI, the stated Washington base income after applicable modifications, and no deductions other than the adjusted standard deduction or credits.
| Calculation | Example 1 | Example 2 |
|---|---|---|
| Federal AGI | $4,000,000 | $4,000,000 |
| Washington base income | $2,000,000 | $500,000 |
| Deduction ratio | 50% | 12.5% |
| Adjusted deduction | $500,000 | $125,000 |
| Washington taxable income | $1,500,000 | $375,000 |
| Tax at 9.9%, before credits | $148,500 | $37,125 |
Example 1 assumes $2 million belongs in Washington base income and $2 million is non-Washington-source income from the nonresident period. Example 2 assumes only $500,000 belongs in Washington base income, with $3.5 million of non-Washington-source income recognized after residency ends.
The $111,375 difference depends on those facts. A bonus for Washington services can remain Washington-source compensation even if paid after departure. These are income-tax illustrations, not estimates for a long-term stock sale.
Keeping a Washington home needs separate review
RCW 82A.04.010(8)(c) applies to someone who first qualifies as a resident under subsection (a). It describes the resident portion by reference to Washington domicile or maintaining a Washington abode.
For someone domiciled here during the move year, that language creates a risk that retaining an abode extends the resident portion beyond the domicile-change date. Treat this as an interpretive issue to resolve on the actual facts, not a settled rule that owning any Seattle condo automatically makes the entire year resident.
In a year with no Washington domicile at any time, the non-domiciliary test requires both a Washington abode and more than 183 Washington days. The separate domiciliary exception requires no permanent Washington abode throughout the year, a permanent abode elsewhere throughout the year, and no more than 30 Washington days. Any portion of a calendar day counts. See the 30-day rule guide.
Calculate long-term stock gains separately
For personally held stock, the capital gains allocation rule looks to domicile when the sale or exchange occurs. Identify that event rather than assuming the cash-payment date controls. The new income tax separately modifies federal long-term gains and losses and provides a credit for Washington capital gains tax.
Do not apply the table above directly to gross stock-sale proceeds or infer that changing domicile resolves every income-tax question. See the two-tax calculation for the addback, deduction, and credit mechanics.
Build a move-year calculation
List expected income events, establish the resident periods, determine each item’s character and source, and apply the deduction ratio. Preserve the move, housing, work-location, and transaction records supporting those inputs. Review guidance applicable to the filing year before relying on a proposed treatment.
For help reviewing your timeline and assumptions, book a 20-minute call with Joe Wallin.
Last reviewed: September 10, 2026. General educational information, not legal or tax advice for a particular move.
