As far as I know, WI follows the federal on the S Corp Health Insurance, but maybe someone else knows for sure. I don't have any S Corps with health insurance.
WI Payroll: WT-6 Payroll WIthholding Monthly, Quarterly or Annual depending on amount.
WT-7 Annual reconciliation
W-2 and if on paper, a WT-2 Transmittal
available here: http://www.revenue.wi.gov/
State Unemployment: Pretty low threshold, I THINK 2 persons and the definition is more aggressive than for income tax. Independent contractors can and have been reclassified as employees for UCI. There is a new employer rate for the first couple of years until the employer gets established.
more info here: https://dwd.wisconsin.gov/ui/
Jill