My question is not about withholding state income tax, it's about whether or not my employer in Wisconsin would be subject to Illinois income or sales tax on sales in Illinois.
so, they don't want you to sell anything in Illinois because they are worried it would subject them to Illinois tax? Are there other states they don't want you to sell products in so as to prevent incurring taxes in those states?
cbg
It's not just state taxes though. It's unemployment and workers compensation and possibly their health insurance and probably a few other things I'm not remembering at the moment.
Health insurance can be purchased, or not purchased, wherever the employer chooses. WC is based on Wisconsin in this situation because that is where the OP would be employed. The business does not maintain a business presence in Illinois so they do not purchase Illinois anything.
The employer can pay unemployment to whatever state they choose but will likely pay it to Wisconsin. Since the OP would be employed in Wisconsin, he could file in Wisconsin or his home state with an interstate claim. The money would be transferred to the Illinois coffers once he files in Illinois.
I am in a similar situation with a couple of neighboring states. In fact, a couple that happen to have reciprocal agreements with both of the OP's states regarding taxation but some of this is irrelevant to the OP's situation because of the lack of a business presence in a state outside of Wisconsin.
The employee would be employed in Wisconsin regardless of him having a home office.
and I LTDT (live there doing that). I live < 1 mile from a state border. My union hall (who purchases our med insurance) is in the other state but they have purchased insurance both in my state and their state. There is no requirement you purchase it in any particular state, especially since there is no requirement you purchase any at all. (with the possible exception of the ACA deal. that one I'll admit I am ignorant on)
WC is based on employers location, even if we travel to the neighboring state. Hell, I have friends that have traveled to 20+states. Do you think the local employer (here) they are working for has to purchase medical and WC insurance in every state they work in?
Unemployment; an employer can choose to pay to the employees home state or the employers state. Most pay to the employers state.