If you are a resident of another state and worked in Wisconsin during the tax year - you are required to file a Wisconsin income tax return and pay Wisconsin income tax on employee compensation for work performed in Wisconsin.

If you are an Wisconsin resident but worked in another state - all of your income is subject to Wisconsin tax, except income earned from out-of-state business activity.

A nonresident is an individual who is not domiciled in Wisconsin for any part of the taxable year. Your domicile is your true, fixed, and permanent home where you intend to remain permanently and indefinitely and to which, whenever absent, you intend to return. It is often referred to as "legal residence." You can be physically present or residing in one state but maintain a domicile in another. You can have only one domicile at any time.

Your domicile, once established, is never changed unless all three of the following occur or exist:

• You specifically intend to abandon your old domicile and take actions consistent with such intent, and
• You intend to acquire a new domicile and take actions consistent with such intent, and
• You are physically present in the new domicile.

Your domicile does not change if:

• You leave your state of domicile for a brief rest or vacation, or
• You leave your state of domicile to complete a particular transaction, perform a particular contract, or fulfill a particular engagement, but you intend to return to your state of domicile whether or not you complete the transaction, contract, or engagement.

Please see for reference - http://www.dor.state.wi.us/pubs/pb122.pdf