2016 Wisconsin corporate and partnership tax return due dates

On Thursday, March 9, Governor Scott Walker signed 2017 Wisconsin Act 2 which conforms Wisconsin due dates with federal due dates for corporate and partnership income and franchise tax returns, as well ​as estimated tax payments. The charts below show the due dates for 2016 tax returns affected by the Act.

2016 Wisconsin Tax Return Due Dates
FormDue Date 4
Form 2: Estates and trusts
Unextended Due Date 1
Extended Due Date
April 18, 2017
October 2, 2017
Form 3: Partnership
Unextended Due Date 1
Extended Due Date 1
April 18, 2017 5
September 15, 2017
Form 4/6: Corporation
Unextended Due Date
Extended Due Date 2
April 18, 2017
November 15, 2017
Form 4/6: Corporation (fiscal year end 6/30)
Unextended Due Date
Extended Due Date 2
September 15, 2017
May 15, 2018
Form 4/6: Corporation (fiscal year)
Unextended Due Date
Extended Due Date 2
15th day of 4th month
15th day of 11th month
Form 4T: Exempt Corporation
Unextended Due Date 1
Extended Due Date 1
May 15, 2017
December 15, 2017
Form 4T: Exempt Fiduciary
Unextended Due Date 1
Extended Due Date
April 18, 2017
October 2, 2017
Form PW-1: Filed by Partnerships
Unextended Due Date
Extended Due Date 3
April 18, 2017 5
October 16, 2017
2017 Corporate Estimated Tax Due Dates 4
Calendar or Fiscal Year
Beginning on or After January 1, 2017,
Exception: Fiscal Year Beginning in April 2017		Fiscal Year Beginning in April 2017
April 18, 2017
(15th day of the 4th month)		June 15, 2017
June 15, 2017
(15th day of the 6th month)		September 15, 2017
September 15, 2017
(15th day of the 9th month)		December 15, 2017
December 15, 2017
(15th day of the 12th month)		March 15, 2018
  1. For fiscal filers, substitute the 15th day of the appropriate month.
  2. Corporations have an automatic seven-month extension, but an extension granted by law or by the IRS extends the time for filing to 30 days after the federal due date.
  3. The Wisconsin statutes provide an automatic seven-month extension.
  4. If the due date falls on a holiday or weekend, the due date is the next business day.
  5. The Act changes the due date to March 15, however since the Act was signed close to the due date, the department will accept as timely 2016 returns and payments filed and paid by the due date under prior law (April 18, 2017).