Wisconsin

Corporate income tax

Corporation franchise or income tax return is due on the federal due date (s. 71.24(1)); generally the 15th day of the 4th month following the close of the taxable year. Exception: fiscal years ending June 30 are due the 15th day of the 3rd month after year end.

Extension. Any extension allowed by the IRS for the federal return automatically extends the Wisconsin due date to 30 days after the federal extended due date...

Partnerships and S corporations

Elective pass-through entity-level tax: partnerships under s. 71.21(6)(a) and tax-option (S) corporations under s. 71.365(4m)(a) may elect to pay tax at the entity level at 7.9% of net income reportable to Wisconsin; requires consent of holders of more than 50% of capital and profits (partnerships) or more than 50% of shares (S corps); election is made annually on or before the due date or extended due date of the return by checking the election box on Form 3 (box I, with Schedule 3-ET) or Form 5S (box A7, with Schedule 5S-ET). Available for taxable years beginning on or after Jan. 1, 2019 (partnerships) and 2018 (S corps). Economic development surcharge: for taxable years beginning on or after Jan. 1, 2013 it does NOT apply to partnerships or LLCs treated as partnerships; it DOES apply to tax-option (S) corporations with gross receipts from all activities of $4,000,000 or more (greater of $25 or 0.2% of Wisconsin net income, max $9,800), reported on Form 5S and due on the unextended return due date. Composite returns Form 1CNP (partnerships, due 15th day of 4th month) and Form 1CNS (S corps) are optional for nonresident owners.

Sales and use tax

Due date. Returns and payment are due the last day of the month following the end of the reporting period (monthly, quarterly, or annual). Exception: early monthly filers must file by the 20th of the month following the end of the reporting period. Electronic returns must be received by 4:00 p.m. CST on the due date; a due date falling on a weekend or legal holiday moves to the next business day. Calendar-year annual filers: January 31.

Filing frequency. Reporting period is early monthly, monthly, quarterly, or annual, as determined and assigned by the Department of Revenue (s. 77.58; Form S-203). Statutory default is quarterly; DOR may require monthly filing by written notice if tax for any calendar quarter exceeds $1,200, and may require filing/payment by the 20th (early monthly) if tax for any calendar quarter exceeds $3,600. DOR may also require returns for periods other than quarterly (annual) under s. 77.58(5). A return must be filed for every assigned period even if no tax is due.

Thresholds. Official (s. 77.58(1) and Publication 201): monthly if tax exceeds $1,200 per quarter; early monthly (due the 20th) if tax exceeds $3,600 per quarter. The annual-filer threshold is not stated on any official page fetched; secondary sources (Quaderno, AccurateTax) state annual filing if $600 or less per year and quarterly if $601 to $1,200 per quarter.

Prepayments. No prepayment or accelerated-payment requirement found on official pages; the only acceleration is the early-monthly (20th of the month) due date for filers with more than $3,600 tax per quarter. (TaxJar loosely calls the early-monthly 20th due date a 'prepayment'; it is a return due date, not a prepayment.)

Notes

Wisconsin has no separate franchise/minimum tax beyond the corporation franchise or income tax (7.9% flat) and the economic development surcharge; corporate annual reports are filed with the Department of Financial Institutions, not DOR, and were not researched. Publication 401 (01/26) and Publication 400 (02/26) are current; Publication 201 is dated 1/19.