Tax returns—Separate and joint returns.

(1) If the federal income tax liabilities of both spouses are determined on a joint federal return for the taxable year, they must file a joint return under this chapter.(2) Except as otherwise provided in this subsection (2), if the federal income tax liability of any individual, including either spouse of a marital community, is determined on a separate federal return for the taxable year, they must file separate returns under this chapter. State registered domestic partners may file a joint return under this chapter even if they filed separate federal returns for the taxable year.(3) The liability for tax due under this chapter of each spouse or state registered domestic partner is joint and several, unless:(a) The spouse or state registered domestic partner is relieved of liability for federal tax purposes as provided under sections 66 or 6015 of the internal revenue code; or(b) Regardless of whether the spouse or state registered domestic partner qualifies for relief as provided under (a) of this subsection (3), the department determines that the spouse or state registered domestic partner qualifies for relief as provided by rule of the department in a manner consistent with sections 66 or 6015 of the internal revenue code.(4)(a) Unless the context clearly indicates otherwise, individuals who are spouses or state registered domestic partners are not considered separate taxpayers for the purposes of this chapter regardless of whether they file a joint or separate return for the tax imposed under this chapter. The activities and assets of each spouse or state registered domestic partner are combined as if they were one individual for the purposes of determining the applicability of any threshold amounts, caps, deductions, credits, or any other amounts related to the activities or assets of an individual throughout this chapter.(b) When an individual does not file a joint return for the tax imposed under this chapter, both spouses or state registered domestic partners must allocate between themselves their respective share of the marital community's or domestic partnership's income, gains, losses, deductions, and credits in a manner consistent with the community property laws of this state and the applicable provisions of the internal revenue code, and its accompanying regulations, addressing taxpayers domiciled in community property jurisdictions.[ 2026 c 238 s 703.]Notes:Findings—Intent—Effect of invalidation of 2026 c 238 s 201—Automatic expiration date and tax preference performance statement exemption—Necessity of act—Intent—Implementation by department of revenue—2026 c 238: See notes following RCW 82A.04.030.