2027 Wisconsin Tax Deadlines

Last updated: August 5, 2026

Key Wisconsin tax dates at a glance

• April 15, 2027: First Individual estimated payment.
• June 15, 2027: Second Individual estimated payment.
• September 15, 2027: Third Individual estimated payment.
• January 18, 2028: Fourth Individual estimated payment.
• March 15, 2028: Calendar-year tax-option S Corporation Form 5S and Partnership Form 3 returns and payments.
• April 18, 2028: Calendar-year C Corporation Form 4 and Individual returns and payments.
• September 15, 2028: Extended Partnership Form 3 return, file only.
• October 16, 2028: Extended tax-option S Corporation Form 5S and Individual returns, file only.
• November 15, 2028: Extended C Corporation Form 4 return, file only.

When are Wisconsin taxes due in 2027?

Wisconsin 2027 calendar-year S Corporation Form 5S and Partnership Form 3 returns are due March 15, 2028. Calendar-year C Corporation Form 4 and Individual returns are due April 18, 2028.

When is the Wisconsin C Corporation return due?

Wisconsin C Corporations should plan around April 18, 2028, for the calendar-year corporate-facing return, tax, or business-level filing noted in this page.

• Form 4: Wisconsin non-combined corporation franchise or income tax return.
• Wisconsin corporate payment and extension review should be tracked separately from Individual extension work.
• File and pay through Wisconsin My Tax Account.

What are Wisconsin C Corporation extension rules?

The extended filing deadline for the main calendar-year Wisconsin corporate-facing return is November 15, 2028. The extension is to file only, and tax or required payments remain due by April 18, 2028.

When are Wisconsin S Corporation and Partnership returns due?

Wisconsin S Corporations should plan around March 15, 2028, and Partnerships should plan around March 15, 2028.

Which Wisconsin pass-through forms are required?

Use the applicable Wisconsin pass-through return and related payment or owner-reporting forms for the entity type and election facts.

• Form 5S: Wisconsin tax-option S Corporation return.
• Form 5S generally receives the federal extension plus 30 days for Wisconsin filing.
• Form 3: Wisconsin Partnership return.
• Form 3 generally follows the federal six-month Partnership extension.

What are Wisconsin pass-through extension rules?

The extended filing deadline for calendar-year Wisconsin S Corporation and Partnership returns is October 16, 2028, for Form 5S filers and September 15, 2028, for Form 3 filers. The extension is to file only, so tax, withholding, composite, or entity-level payments should be handled by the original deadline.

When is the Wisconsin Individual income tax return due?

Calendar-year Wisconsin Individual income tax returns and payments are due April 18, 2028.

• Form 1: Wisconsin resident Individual income tax return.
• Form 1NPR: Wisconsin nonresident and part-year resident return.

What Wisconsin Individual rate and residency issues should be checked?

Tax year 2027 Individual instructions should be checked for final rate tables, standard deductions or exemptions, residency rules, retirement-income treatment, credits, estimated-payment thresholds, and any filing-year changes specific to Wisconsin.

When are Wisconsin estimated payments due?

Wisconsin estimated-payment planning should separate Individual estimates, corporation payments, tax-option S Corporation work, Partnership owner reporting, and extension balances.

• April 15, 2027: First estimated payment.
• June 15, 2027: Second estimated payment.
• September 15, 2027: Third estimated payment.
• January 18, 2028: Fourth estimated payment.

Who must make Wisconsin estimated payments?

Taxpayers should use the final 2027 Wisconsin instructions to confirm estimated-payment thresholds, safe-harbor rules, credits, withholding, pass-through owner treatment, and electronic-payment requirements.

What are Wisconsin extension deadlines?

Wisconsin extension deadlines are October 16, 2028, for Form 5S filers and September 15, 2028, for Form 3 filers for pass-through filings, November 15, 2028, for corporate-facing filings, and October 16, 2028, for Individual returns. Extensions add filing time only; payment deadlines remain tied to the original return due dates.

What Wisconsin-specific rules should tax professionals watch for 2027?

Beyond the core return deadlines, Wisconsin tax professionals should track state-specific rate, credit, local-tax, industry, and filing-method rules before the 2027 season locks.

• Wisconsin corporation franchise or income tax is generally imposed at 7.9%.
• Wisconsin currently uses four Individual rates of 3.50%, 4.40%, 5.30%, and 7.65%.
• Dollar brackets are inflation-adjusted, so use the final 2027 schedule.
• Use Form 3 for Partnerships, not Form 5.
• Separate the Form 5S October 16, 2028, extension from the Form 3 September 15, 2028, extension.
• Confirm the final 2027 Individual bracket thresholds and any enacted rate changes before filing.

Tax-professional context: Beyond the core return deadlines, Wisconsin's tax landscape carries recurring, non-deadline features that shape 2027 planning. The state pairs a graduated Individual income tax with a corporation income or franchise tax and an elective pass-through entity tax, then layers targeted credits and industry incentives on top. The points below summarize what tax professionals most often revisit before the 2027 season locks.

Electronic filing and payment:

• C Corporations and pass-through entities are expected to file and pay through My Tax Account.
• Individuals can file electronically through Wisconsin's online filing options.
• Professional preparers should use Wisconsin-approved software vendors.

Pass-through entity tax election:

• Wisconsin allows tax-option (S) corporations and partnerships to elect an entity-level tax.
• The election shifts tax to the entity level and changes owner reporting and estimated-payment planning.
• Confirm the election mechanics and payment timing in the final 2027 instructions.

Credits and incentives to review:

• Manufacturing and Agriculture Credit.
• Research and Development Credit.
• Historic Rehabilitation Credit.
• Earned Income Tax Credit and Homestead Credit for qualifying Individuals.

Retirement and residency treatment:

• Social Security benefits are generally exempt from Wisconsin income tax.
• Certain military retirement pay may be exempt.
• Qualifying pension income may be excluded; confirm eligibility in the 2027 instructions.

Industry focus:

• Manufacturing (including advanced manufacturing and R and D activity).
• Agriculture and dairy.
• Technology and university research partnerships.

Wisconsin's separate Form 5S and Form 3 extension calendars can trip up pass-through work, so firms can find specialists through the accounting firm directory.

What sources support these Wisconsin dates?

• Wisconsin tax rates.
• Wisconsin extensions of time to file.
• Wisconsin corporation forms and instructions.
• Wisconsin estimated income tax.

Separate Wisconsin entity extension calendars

Instead's AI-driven tax platform helps Wisconsin teams coordinate return work, payment review, extensions, and filing follow-through before deadlines move from planning to execution.

For Wisconsin practices, workflows, estimates, and tax preparers help connect research, planning, and operational handoffs without duplicating deadline data. Built for tax professionals who want source-backed state deadline control across clients, entities, and reviewer workflows.