Wisconsin Tax Deadlines
State income tax filing deadlines, extensions, and estimates for 2026.
Wisconsin Department of Revenue
https://www.revenue.wi.gov
individual deadline
Due: Apr 15, 2026
Extension: Oct 15, 2026
Form: Form 1
WI returns due April 15, 2026; federal extension applies to WI.
Estimated Payments
Sole Proprietorship deadline
Due: Apr 15, 2026
Extension: Oct 15, 2026
Form: Form 1
Business income reported on WI personal return.
Estimated Payments
Partnership deadline
Due: Mar 16, 2026
Extension: Sep 15, 2026
Form: State business income tax return
Calendar-year due date follows federal timing for pass-through entities.
S Corporation deadline
Due: Mar 16, 2026
Extension: Sep 15, 2026
Form: State business income tax return
Calendar-year due date follows federal timing for pass-through entities.
C Corporation deadline
Due: Apr 15, 2026
Extension: Oct 15, 2026
Form: State corporate income tax return
Calendar-year due date follows federal timing for corporations.
Estimated Payments
LLC deadline
Due: Mar 16, 2026
Extension: Sep 15, 2026
Form: State business income tax return
Calendar-year due date follows federal timing for pass-through entities.
Nonprofit deadline
Due: May 15, 2026
Extension: Nov 15, 2026
Form: State nonprofit return
Nonprofit annual return generally due the 15th day of the 5th month.
Estimated Tax Payments
View all quarterly estimated payment due dates for Wisconsin.
FAQ
Does Wisconsin conform to federal due dates?
Many Wisconsin deadlines follow the federal calendar. Always confirm on Wisconsin Department of Revenue.
Where can I file Wisconsin tax forms?
Visit Wisconsin Department of Revenue at https://www.revenue.wi.gov for official forms and e-file options.