Is Washington state workers compensation disability insurance taxable?

Workers compensation is non-taxable income.

Generally, most income you receive is considered taxable but there are situations when certain types of income are partially taxed or not taxed at all. Amounts you receive as workers' compensation for an occupational sickness or injury are fully exempt from tax if they are paid under a workers' compensation act or a statute in the nature of a workers' compensation act. The exemption also applies to your survivors. The exemption, however, does not apply to retirement plan benefits you receive based on your age, length of service, or prior contributions to the plan, even if you retired because of an occupational sickness or injury.

Please see the following link for more information IRS Publication 525 (click here)