RCW 82.87.060: Deductions.

In computing tax for a taxable year, a taxpayer may deduct from his or her Washington capital gains:

(1) A standard deduction of $250,000 per individual, or in the case of spouses or domestic partners, their combined standard deduction is limited to $250,000, regardless of whether they file joint or separate returns. The amount of the standard deduction shall be adjusted pursuant to RCW 82.87.150;

(2) Amounts that the state is prohibited from taxing under the Constitution of this state or the Constitution or laws of the United States;

(3) The amount of adjusted capital gain derived from the sale or transfer of the taxpayer's interest in a qualified family-owned small business pursuant to RCW 82.87.070; and

(4) Charitable donations deductible under RCW 82.87.080.