Q. Does this mean any income earned in Washington will be fully taxed by Nebraska?
A. Yes, starting on the date of the move to NE.
You report all your income on your resident state return, including the income earned in another state. Your home state calculates tax on all your income, but gives you a credit, or partial credit, for tax you paid to the other state.
When you worked in a state without an income tax (e.g. Washington), there will be no credit, since there was no WA tax. In other words, having worked in a state without an income tax does not get you out of paying state tax, on that income, to your home state.
