Business Income/Franchise Tax Late-Filed Returns

1. ​​What if my electronically filed return is rejected on the due date of the return?
2. Am I subject to interest or penalties if I don't file my Wisconsin income tax return by the due date?
3. Will I be assessed a late filing fee if I qualify for an extension of time to file?

1. What if my electronically filed return is rejected on the due date of the return?

   If an electronically filed return is rejected, you must correct the errors and resubmit the return within five business days of the rejection for the return to still be considered timely (called the "perfection period").

2. Am I subject to interest or penalties if I don't file my Wisconsin income tax return by the due date?

   If your business income/franchise tax return is not filed by the appropriate extended due date, you may be subject to the following charges:

   • Late-filing fee: $150 for corporation income or franchise returns (Forms 4, 4T, 5S, and 6), $50 for partnership returns (Form 3), $50 for fiduciary income tax returns (Form 2 and 4T), and $50 per shareholder for composite income tax returns (Form 1CNS and 1CNP)
   • Delinquent interest: 1.5% per month (18% per year)
   • Negligence penalty for failure to timely file: 5% per month of the tax required to be shown on the return, up to a maximum of 25%
     
     
3. Will I be assessed a late filing fee if I qualify for an extension of time to file?

   Wisconsin generally allows the same extension periods as allowed for federal tax. You will not be assessed a late filing fee if you file within the extension period. You may be assessed interest if tax is due.

Applicable Laws and Rules

This document provides statements or interpretations of the following laws and regulations enacted as of February 20, 2026: chs. 71 and 77, Wis. Stats., and chs. Tax 1, 2, 3, and 11 Wis. Adm. Code.

Laws enacted and in effect after this date, new administrative rules, and court decisions may change the interpretations in this document. Guidance issued prior to this date, that is contrary to the information in this document is superseded by this document, according to sec. 73.16(2)(a), Wis. Stats.

The department welcomes your input on our guidance. Submit comments on this guidance document.

Guidance Document Number: 100323

February 20, 2026