Wisconsin Administrative Code
Department of Revenue
Chapter Tax 2 - Income Taxation, Returns, Records And Gross Income
Section Tax 2.96 - Extensions of time to file corporation franchise or income tax returns

(a) General. Except as provided in pars. (am) and (b), corporation franchise or income tax returns are due on or before the 15th day of the 4th month following the close of a corporation's taxable year unless an extension of time for filing has been granted.

(am) For tax exempt corporations with unrelated business taxable income, the franchise or income tax return is due on or before the 15th day of the 5th month following the close of the corporation's taxable year unless an extension of time for filing has been granted.

(b) Short-period returns. Corporation franchise or income tax returns for periods of less than 12 months are due on or before the federal due date.

(a) Automatic extension. For corporation franchise or income tax returns, an automatic extension is allowed for a period of 7 months or until the original due date of the corporation's corresponding federal return, whichever is later. If any extension is obtained for federal purposes, that extension also applies for Wisconsin purposes and is further extended for another 30 days after the federal due date. A copy of federal extension form 7004, or other federal extension form, if applicable, shall be attached to any Wisconsin franchise or income tax return filed under extension, even if the extension was not requested for federal purposes.

(b) Combined returns. For corporations required to use combined reporting under s. 71.255, Stats., any extension granted to the designated agent of the combined group is considered granted to each corporation in the combined group.

(c) Estimated tax payment. A taxpayer who desires to minimize interest charges during the extension period may pay the estimated tax liability on or before the original due date of the franchise or income tax return. The estimated tax liability includes the economic development surcharge imposed under s. 77.93, Stats.

Note: See s. Tax 2.66 for rules relating to the payment of estimated taxes by combined groups.

(a) Regular interest. Except as provided in par. (b), additional tax due with the complete return and the economic development surcharge imposed under s. 77.93, Stats., which are not paid by the original due date are subject to interest at 12% per year during the extension period and 1 1/2% per month from the end of the extension period until the date of payment.

(b) Delinquent interest. If 90% of the tax shown on the return is not paid by the unextended due date of the return, the difference between that amount and the estimated taxes paid along with any interest due is subject to interest at 1 1/2% per month until paid regardless of any extension granted for filing the return. The tax shown on the return includes the economic development surcharge imposed under s. 77.93, Stats.

(c) Late filing fee. A corporation return filed after the extension period is subject to a $150 late filing fee.