Understand the difference between flat and progressive state income tax systems. Learn how each type of tax structure impacts your annual tax bill and financial planning.

Dec. 9—Over the past four years, four states have abandoned progressive income-tax formulas to embrace a flat income-tax rate like that in Illinois. That brings the number of flat-tax states to 14, ...

If you’ve ever noticed that higher earners pay a higher tax rate than lower earners, you’ve already encountered a progressive tax system. In simple terms, a progressive tax is designed so that tax ...