All residents in this state pay 3.07% on earned income. Pennsylvania is the state with the lowest flat state income tax rate. Here's a closer look at the states with the lowest flat state income tax rates based on current tax rates. The states with the lowest flat state income tax rates Washington: Residents are responsible for paying a 7% tax on the sale or exchange of long-term capital assets if their profits exceed $250,000 annually. New Hampshire: Residents pay a tax rate of 5% on interest and dividends. SUBSCRIBE TO OUR NEWSLETTER: The Daily Money delivers our top personal finance stories to your inbox

They do, however, impose a flat rate tax for other tax situations. These two states don't levy state income tax on regular earned income. There are two other states worth mentioning in this discussion: New Hampshire and Washington. That means residents with low incomes and high incomes all pay taxes at the same rate. Nine states have a flat tax rate for all residents. But tax rates can differ significantly from state to state. Paying state and federal taxes on earned income is the norm for many Americans. Watch Video: What you need to know about cryptocurrency and filing your taxes

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