Wisconsin Filing Due Date: Corporation tax returns are due by March 15 — or by the 15th day of the 3rd month following the end of the taxable year (for fiscal year filers).
Extended Deadline with Wisconsin Tax Extension: If you have an approved Federal tax extension (IRS Form 7004), your Wisconsin filing deadline will be automatically extended to 30 days past the Federal extension deadline. For example, if a Federal extension gives a corporation until September 15 to file its Federal return, that means it has until October 15 to file its Wisconsin return.
For corporations without a Federal extension, Wisconsin offers an automatic state-only tax extension of 7 months or until the original deadline of the corporation’s corresponding Federal return, whichever is later.
Wisconsin Tax Extension Form: Wisconsin tax extensions are automatic, which means there’s no state-specific application or written request to submit. You can use IRS Form 7004 to apply for a Federal tax extension and receive an automatic Wisconsin tax extension.
Wisconsin Extension Payment Requirement: An extension of time to file is not an extension of time to pay. If you owe Wisconsin tax, it must be paid by the original due date to avoid penalties and interest. You can make a state extension payment using Wisconsin Form 4-ES.
Wisconsin Tax Extension Tips: Partnership tax returns are due by April 15 — or by the 15th day of the 4th month following the end of the taxable year (for fiscal year filers). Wisconsin offers a 5-month extension for partnerships, which moves the filing deadline to September 15 (for calendar year filers).