Small Business Tax Deadlines Every Wisconsin Owner Should Know
- Allison Sikorsky
- Jun 6
- 2 min read
Updated: Jun 10
Whether you run a cozy coffee shop in Door County, a boutique in Green Bay, or a mobile grooming service out of Kewaunee, staying on top of your tax deadlines isn’t just a best practice—it’s essential to keeping your business in good standing (and avoiding late fees or penalties).
This quick guide breaks down the key 2025 tax deadlines that Wisconsin small business owners need to know, whether you're a sole proprietor, LLC, or S corporation.
Key 2025 Federal Tax Deadlines
January 31, 2025
Deadline to send W-2s and 1099-NECs to employees and independent contractors
File 1099s with the IRS via paper or electronically
Great time to close out prior-year bookkeeping
March 15, 2025
Partnership and S-Corporation returns due (Forms 1065 & 1120S)
If applicable, this is also the due date for filing K-1s to members/shareholders
File for an extension (Form 7004) if needed
April 15, 2025
Deadline for sole proprietors, single-member LLCs, and C corporations
Personal tax returns (Form 1040) due
1st quarter estimated tax payment due (Form 1040-ES)
June 15, 2025
2nd quarter estimated tax payment due
September 15, 2025
3rd quarter estimated tax payment due
Extended deadline for S-Corps and Partnerships if you filed Form 7004
October 15, 2025
Extended deadline for personal returns (Form 1040) and C Corporations
Final call for Schedule C filers who filed for an extension
Wisconsin-Specific Deadlines
Wisconsin Annual Report
Most LLCs and corporations must file an Annual Report with the Wisconsin Department of Financial Institutions (WDFI)
Due by the end of the quarter in which your business was formed(Example: If you formed your LLC in May, your Annual Report is due by the end of Q2 each year—June 30.)
File online at www.wdfi.org
Sales Tax Filing (Wisconsin Department of Revenue)
Monthly, quarterly, or annual depending on your filing frequency
Common due dates:
Monthly: 20th of each month
Quarterly: April 20, July 20, October 20, January 20
Annually: January 20 for prior year
Pro Tip: Double-check your assigned frequency through the WI DOR's My Tax Account.
Bonus Tip: Set a Calendar Reminder
We recommend plugging these deadlines into your calendar now (with a little buffer) and syncing them with your bookkeeping schedule.
Not Sure What Applies to You?
If you’re not sure which deadlines apply to your business—don’t guess. Whether you’re running payroll, collecting sales tax, or trying to figure out if you need to file a 1099, we’re here to help you get it right.
Let’s Make It Easy
At Curated Accounting Solutions, we specialize in helping small businesses across Door, Kewaunee, and Brown Counties stay compliant without the stress. From W-2s to quarterly estimates, we’ll help you stay ahead of the deadlines—and give you your time back.
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