One of the great mysteries that will unfold if NH passes an Income Tax is the tax credit for taxes paid to another state. There appear to be several alternatives in play.
1- On your NH income tax return you get credit for taxes paid to another state ie Mass Maine Vt , where you work and the taxes are withheld.
2- The state where you work allows a credit for taxes paid to NH on their non resident returns
My curious mind wonders if Mass, Maine and Vt, would actually agree to loose all that wonderful tax revenue option 2 involves. My bet is that NH is faced with Option 1, where if you work in another state, they get the tax and the burden of income tax is placed squarely on people who work in NH

. I do not know how much tax money is paid to Mass and Maine by NH residents but I bet it is substantial.