My son still has his driver's license and license plates from IL even though he is now working in Wisconsin. Is he still considered a resident of Wisconsin?

[tygrtchr]

If he has not transferred his drivers' license and plates (and, possibly, voter registration) to Wisconsin, he is still considered a resident of Illinois and would file as a non-resident in Wisconsin.  He may have to file IL taxes and show what he paid in Wisconsin.  This varies by state.

[pk]

generally, driver's license, voter's reg  etc are used to determine the residency of the taxpayer -- closer connection.

Additionally IL and WI being reciprocal state, the state of residency taxes income ( generally wages/self-employment etc. ) no matter where earned.