Wisconsin Business Tax Deadlines (2026)
Next: May 15 — Form 990 due for nonprofits
Next Deadline: May 15 — Form 990 due for nonprofits
Federal Tax Deadlines (2026)
| Form | Who Files | Due Date | Extension Deadline |
|---|---|---|---|
| Form 1040 (Schedule C) | Sole proprietors | April 15 | October 15 |
| Form 1065 | Partnerships, Multi-member LLCs | March 15 | September 15 |
| Form 1120-S | S-Corporations | March 15 | September 15 |
| Form 1120 | C-Corporations | April 15 | October 15 |
| Form 990 | Nonprofits | May 15 | November 15 |
| Estimated Taxes (Q1-Q4) | All | Apr 15, Jun 15, Sep 15, Jan 15 2027 | — |
Wisconsin State Tax Deadlines (2026)
| Tax Type | Who Files | Due Date | Extension Deadline |
|---|---|---|---|
| Individual Income Tax (Form 1) | Individuals, sole proprietors | April 15 | October 15 |
| Estimated Income Tax (Q1-Q4) | Individuals owing $200+ | Apr 15, Jun 15, Sep 15, Jan 15 2027 | — |
| Corporate Franchise/Income Tax (Form 4) | C-Corporations | April 15 (calendar year) | October 15 |
| S-Corp Return (Form 5S) | S-Corporations | March 15 | September 15 |
| Partnership Return (Form 3) | Partnerships | March 15 | September 15 |
| Sales & Use Tax | Businesses with taxable sales | Monthly (20th), quarterly, or annual | — |
| Payroll — Employer Withholding | Employers | Monthly, quarterly, or annual | — |
| Annual Report | Corporations and LLCs | Annually (March 31 for corps, quarter anniversary for LLCs) | — |
Quarterly Estimated Tax Deadlines in Wisconsin
Wisconsin follows the federal estimated tax schedule:
| Quarter | Due Date |
|---|---|
| Q1 | April 15 |
| Q2 | June 15 |
| Q3 | September 15 |
| Q4 | January 15, 2027 |
Estimated payments are required if you expect to owe $200 or more in Wisconsin income tax after withholding and credits — one of the lower thresholds in the nation.
Wisconsin-Specific Tax Requirements
Wisconsin imposes a graduated individual income tax with four brackets: 3.5% on the first $14,320 (single), 4.4% on $14,321–$28,640, 5.3% on $28,641–$315,310, and 7.65% on income over $315,310. The top rate of 7.65% is among the higher rates in the Midwest. Business income from sole proprietorships and pass-through entities is taxed at individual rates. Wisconsin does not currently offer a PTE-level tax election.
The Corporate Franchise/Income Tax is a flat 7.9% on net income apportioned to Wisconsin — one of the higher corporate tax rates nationally. The franchise tax and income tax are effectively combined into one return. There is no separate franchise tax base; the 7.9% rate applies to net income. A minimum tax of $25 applies to all corporations.
Wisconsin's Sales and Use Tax has a state rate of 5%, with county additions of 0.5%–1.75% (most counties impose 0.5%), bringing combined rates typically to 5.5%–5.5% (Milwaukee County is 5.5%). Some counties have adopted a 0.75% or higher rate. Monthly returns are due by the 20th of the following month. Wisconsin taxes most tangible goods and selected services. Employers must withhold Wisconsin income tax and can file monthly, quarterly, or annually depending on their withholding amount. The Annual Report for corporations is due March 31 ($25 filing fee); LLCs file during their anniversary quarter ($25 fee).
What Happens If You Miss a Wisconsin Tax Deadline?
Wisconsin's late filing penalty is 5% per month of the unpaid tax, up to a maximum of 25%. If the return is more than 60 days late, the minimum penalty is the lesser of $100 or the full tax due. A late payment penalty of 1% per month of the unpaid balance also applies, up to 18%.
Interest on underpaid taxes accrues at a rate set semiannually — for 2026, approximately 8%–9% per year (calculated as 6% plus the federal short-term rate, with a 6% floor). A negligence or fraud penalty of 25%–100% may be added for intentional non-compliance.
Wisconsin grants a 7-month automatic extension for individual income tax (file by October 15) and a 7-month extension for corporate returns, but you must pay at least 90% of the total tax liability by the original due date to avoid late payment penalties. If you have a valid federal extension, Wisconsin automatically extends your filing deadline. Sales tax returns cannot be extended.
Wisconsin Department of Revenue
---
> Books behind before a deadline? Ketchup catches up your QuickBooks in 3–7 business days. Get your price →
Related Resources
Behind on Wisconsin taxes?
Accounting Ketchup catches up your QuickBooks so you can file on time.