Do I really owe an underpayment penalty for Kansas if I’m a KS resident but earned no money in Kansas?

If you are a Kansas resident you have to pay Kansas tax on all of your income, no matter where the income is from. If you did not pay enough Kansas tax during the year, through either withholding or estimated tax, then you will owe an underpayment penalty.

Q. Do I really owe an underpayment penalty for Kansas if I’m a KS resident but earned no money in Kansas?

A.  Yes. If your employer was not withholding KS tax, your were expected to make quarterly estimated payments to KS. 

You report all your income on your resident state return, including the income earned in the other 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.  Florida), there will be no credit, since there was no FL 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.