The state of Washington is one of only seven in the U.S. that does not have a state income tax. Washingtonians have rejected the notion of a state income tax time and time again. Seven times since 1933, in fact. By virtue of that, quite possibly, a more regressive system of taxation to generate revenue has emerged.
A recent study by ITEP (Institute on Taxation & Economic Policy) entiled "Who Pays? A Distributional Analysis of the Tax Systems In All 50 States" found that the state of Washington ranks dead last among all 50 states for the tax burden that is levied on the poor and nearly last for the middle class.

Low-income earners in Washington ($25,000 or less) rank 51st -- dead last -- for the amount of the tax burden imposed on them as a percentage of income, with 14.5 cents of every dollar going to taxes, user fees, etc.

It's not much better for the middle class in the Evergreen State. Those making $50,000 or less pay 11 cents per dollar to fund their share of the state's government -- 48th out of 51.

High-income earners ($150,000) rate much, much better -- 13th overall at 7.3 percent.
Source: WalletHub
Source: WalletHub