Wisconsin — Corporate Income / Franchise Tax

Wisconsin imposes both a franchise tax and a corporate income tax on corporations. The franchise tax applies to every domestic or foreign corporation doing business in Wisconsin in a corporate capacity or exercising its franchise within the state, except for corporations specifically exempted under Wis. Stat. § 71.26(1). The tax is measured by the corporation's entire Wisconsin net income of the preceding taxable year and is computed at a rate of 7.9 percent.

Every corporation organized under Wisconsin law is deemed to be residing within Wisconsin for purposes of the franchise tax. The corporate income tax applies only to corporations not subject to the franchise tax that own property in Wisconsin, derive income from sources within the state, or conduct business consisting exclusively of foreign or interstate commerce.

Source: Wis. Stat. § 71.23(2); Wis. Stat. § 71.27(2)

Wisconsin corporate franchise and income tax returns are due on the date the corporation is required to file its federal income tax return (not including any federal extension). For calendar-year C corporations, the federal due date (and thus the Wisconsin due date) remains the 15th day of the 4th month after the close of the taxable year (April 15 for a December 31 year-end), as provided under 26 U.S.C. § 6072(a). In contrast, partnerships and S-corporations (tax-option corporations) file returns by the 15th day of the 3rd month (March 15), under 26 U.S.C. § 6072(b), and Wisconsin conforms to those federal due dates similarly.

Regarding extensions, Wisconsin allows an automatic extension of 7 months or until the original federal due date, whichever is later. If a federal extension is granted, Wisconsin extends the due date to 30 days after the federal extended due date, provided the taxpayer reports the extension as specified by the Department of Revenue. See Wis. Admin. Code § Tax 2.96 and Wis. Stat. § 71.24(1).

Note: The Protecting Americans from Tax Hikes (PATH) Act affects the timing of certain refundable credit refunds but does not change the due dates for filing corporate income tax returns.

Source: Wis. Stat. § 71.24(1), 26 U.S.C. § 6072(a), 26 U.S.C. § 6072(b), Wis. Admin. Code § Tax 2.96

Wisconsin applies a flat 7.9 percent rate to both the corporate income tax and the franchise tax. The corporate income tax is computed at 7.9 percent of Wisconsin net income. The franchise tax, which is imposed under Wis. Stat. § 71.23(2) and measured by Wisconsin net income, is also computed at 7.9 percent.

Source: Wis. Stat. § 71.27(1) and (2)

For tax years beginning after December 31, 2007, Wisconsin apportions the net income of multistate corporations using a single-sales-factor formula. The apportionment fraction is composed solely of the sales factor under Wis. Stat. § 71.25(9). Certain industries—air carriers, financial organizations, telecommunications companies, pipeline companies, public utilities, railroads, and car line companies—apportion income under Department of Revenue rules rather than the standard formula.

Source: Wis. Stat. § 71.25(6)(d)

Wisconsin imposes franchise or income tax filing obligations on foreign corporations (those not organized under Wisconsin law) that are "doing business in this state." The statutory definition of "doing business" includes a broad range of activities, subject to federal constitutional limitations under Public Law 86-272.

Statutory nexus-creating activities

Under Wis. Stat. § 71.22(1r), "doing business in this state" includes, except where prohibited by P.L. 86-272:

• Issuing credit, debit, or travel and entertainment cards to Wisconsin customers
• Regularly selling products or services to customers in Wisconsin that receive the product or service in the state
• Regularly soliciting business from potential customers in Wisconsin
• Regularly performing services outside Wisconsin for which the benefits are received in Wisconsin
• Regularly engaging in transactions with Wisconsin customers that involve intangible property and result in receipts flowing from Wisconsin
• Holding loans secured by real or tangible personal property located in Wisconsin
• Owning, directly or indirectly, a partnership interest (general or limited) in a partnership doing business in Wisconsin, regardless of percentage of ownership
• Owning, directly or indirectly, an interest in an LLC doing business in Wisconsin, regardless of percentage of ownership, if the LLC is treated as a partnership for federal tax purposes

The 15-day rule

Wisconsin applies a specific numerical threshold to determine when activity is "regular" for nexus purposes. Under Wis. Admin. Code Tax 2.82(2)(bm), "regular" and "regularly" mean 15 or more days of activity. Fifteen days of activity means one person for 15 days, or 15 persons for one day, or any combination of persons and days that results in at least 15 person-days of activity. Days of activity include any day, or portion thereof, upon which business activity took place; travel days, holidays, and weekends do not count unless business activities were conducted on those days.

For example, if a foreign corporation sends five employees to Wisconsin for three days each to conduct a training seminar, the corporation has nexus because its employees conducted activity in Wisconsin for 15 person-days (5 × 3 = 15).

Additional regulatory nexus triggers

Wis. Admin. Code Tax 2.82(4)(a) enumerates specific activities that create nexus for unlicensed foreign corporations, including:

• Maintaining a business location in Wisconsin, such as an office, warehouse, repair shop, parts department, purchasing office, employment office, sales office, permanent sample or display room, or research facility
• Ownership of tangible personal property in Wisconsin, including inventory held by a distributor, consignee, or other non-employee representative (excluding personal property for use in an employee's or representative's home, residential office, or automobile that is solely limited to conducting activities protected by P.L. 86-272)
• Regular activity by employees or representatives soliciting orders with authority to approve them
• Operation of mobile stores in Wisconsin, such as trucks with driver-salespersons, regardless of frequency
• Regular delivery of goods into Wisconsin by vehicles owned or leased by the foreign corporation
• Licensing of intangible rights for use in Wisconsin
• Engaging in substantial activities that help to establish and maintain a market in Wisconsin

Domestic corporations and licensed foreign corporations

Every domestic corporation (one organized under Wisconsin law) and every licensed foreign corporation must file a Wisconsin corporate franchise or income tax return, regardless of whether business was transacted, unless exempt under Wis. Stat. § 71.26(1) or § 71.45(1).

Combined-group attribution nexus

For a combined group that has made the controlled group election under Wis. Stat. § 71.255(2m), the entire commonly controlled group's business is deemed to be a single unitary business. If at least one member of the combined group has nexus in Wisconsin, all members of the combined group have nexus in Wisconsin under Wis. Admin. Code Tax 2.82(5).

Source: Wis. Stat. § 71.22(1r); Wis. Admin. Code Tax 2.82(2)(bm); Wis. Admin. Code Tax 2.82(4)(a); Wis. Admin. Code Tax 2.82(5)

Wisconsin applies distinct sourcing rules depending on whether the corporation is selling tangible personal property, services, computer software, or intangible property. Because Wisconsin uses single-sales-factor apportionment for tax years beginning after December 31, 2007, correctly sourcing sales to the Wisconsin numerator is the sole determinant of the apportionment percentage for most corporations.

Tangible personal property — destination sourcing with throwback

Sales of tangible personal property are sourced to Wisconsin under Wis. Stat. § 71.25(9)(b) if any of the following occur:

1. Destination sourcing (non-federal purchasers): The property is delivered or shipped to a purchaser, other than the federal government, within Wisconsin regardless of the f.o.b. point or other conditions of the sale.

1. Federal government sales (in-state delivery): The property is shipped from an office, store, warehouse, factory, or other place of storage in Wisconsin and delivered to the federal government within Wisconsin regardless of the f.o.b. point or other conditions of sale.

1. Federal government sales (throwback rule): The property is shipped from a Wisconsin office, store, warehouse, factory, or other place of storage and delivered to the federal government outside Wisconsin, and the taxpayer is not within the jurisdiction, for income or franchise tax purposes, of the destination state.

1. Non-federal sales (throwback rule): The property is shipped from a Wisconsin office, store, warehouse, factory, or other place of storage to a purchaser other than the federal government, and the taxpayer is not within the jurisdiction, for income or franchise tax purposes, of the destination state.

Under Wis. Stat. § 71.25(9)(c), a "nowhere income" rule applies: sales of tangible personal property sold by a Wisconsin office to a purchaser in another state, where the property is not shipped or delivered from Wisconsin, are sourced to Wisconsin if the taxpayer is not taxable in either the state from which the property is shipped or the destination state. This rule captures sales managed by a Wisconsin office even when fulfillment occurs from an out-of-state location where the taxpayer has no tax presence.

Services — market-based sourcing (effective for tax years beginning after December 31, 2005)

Gross receipts from services are sourced to Wisconsin under Wis. Stat. § 71.25(9)(dh) if the purchaser of the service received the benefit of the service in Wisconsin. This market-based sourcing rule replaced the prior cost-of-performance method. The benefit of a service is received in Wisconsin if any of the following applies:

• The service relates to real property located in Wisconsin.
• The service relates to tangible personal property located in Wisconsin at the time the service is received or tangible personal property delivered to customers in Wisconsin.
• The service is provided to an individual who is physically present in Wisconsin at the time the service is received.
• The service is provided to a person engaged in a trade or business in Wisconsin and relates to that person's business in Wisconsin.

If the purchaser receives the benefit of a service in more than one state, the gross receipts are assigned to Wisconsin based on the portion of the service received in Wisconsin.

Computer software

Gross receipts from the use of computer software are sourced to Wisconsin under Wis. Stat. § 71.25(9)(df) if the purchaser or licensee uses the computer software at a location in Wisconsin. Computer software is used at a location in Wisconsin if the purchaser or licensee uses the computer software in the regular course of business operations in Wisconsin, for personal use in Wisconsin, or if the purchaser or licensee is an individual whose domicile is in Wisconsin.

If the purchaser or licensee uses the computer software in more than one state, the gross receipts must be divided among those states having jurisdiction to impose an income tax on the taxpayer in proportion to the use of the computer software in those states. To determine computer software use in Wisconsin, the Department of Revenue may consider the number of users in each state where the computer software is used, the number of site licenses or workstations in Wisconsin, and any other factors that reflect the use of computer software in Wisconsin.

Intangible property royalties and licenses

Gross royalties and other gross receipts received for the use or license of intangible property—including patents, copyrights, trademarks, trade names, service names, franchises, licenses, plans, specifications, blueprints, processes, techniques, formulas, designs, layouts, patterns, drawings, manuals, technical know-how, contracts, and customer lists—are sourced to Wisconsin under Wis. Stat. § 71.25(9)(dj) if the purchaser or licensee uses the intangible property in the operation of a trade or business at a location in Wisconsin.

If the purchaser or licensee uses the intangible property in the operation of a trade or business in more than one state, the gross royalties and other gross receipts from the use of the intangible property must be divided between those states having jurisdiction to impose an income tax on the taxpayer in proportion to the use of the intangible property in those states.

Broadcaster special rule (effective for tax years beginning after December 31, 2018): A broadcaster's gross royalties and other gross receipts received for the use or license of intangible property are sourced to Wisconsin only if (1) the commercial domicile of the purchaser or licensee is in Wisconsin and (2) the purchaser or licensee has a direct connection or relationship with the broadcaster pursuant to a contract under which the royalties or receipts are derived. This narrower rule applies only to broadcasters; it does not apply to other members of a combined group that are not themselves broadcasters.

Residual rule for other sales (cost-of-performance)

For sales not covered by the specific rules above, Wis. Stat. § 71.25(9)(d) provides that sales other than sales of tangible personal property are in Wisconsin if the income-producing activity is performed in Wisconsin. If the income-producing activity is performed both in and outside Wisconsin, the sales are divided between those states having jurisdiction to tax such business in proportion to the direct costs of performance incurred in each state in rendering the service. This cost-of-performance rule applies only when the market-based sourcing provisions in § 71.25(9)(df), (dh), and (dj) do not apply.

Source: Wis. Stat. § 71.25(9)(b); Wis. Stat. § 71.25(9)(c); Wis. Stat. § 71.25(9)(d); Wis. Stat. § 71.25(9)(df); Wis. Stat. § 71.25(9)(dh); Wis. Stat. § 71.25(9)(dj)

Wisconsin imposes an economic development surcharge on certain business entities, including most corporations and insurance companies, with gross receipts of $4 million or more in a taxable year. The surcharge was first imposed for taxable years beginning on or after January 1, 2008, but the current $4 million gross receipts threshold has applied since taxable years beginning on or after January 1, 2013. The surcharge is calculated and reported as part of the Wisconsin corporate/franchise tax return.

Who is subject: The surcharge applies to C corporations, insurance companies, and also tax-option (S) corporations, though the calculation differs for S corporations. It does not apply to sole proprietorships, partnerships, estates, trusts, or limited liability companies taxed as partnerships or disregarded entities. Certain exemptions may apply to not-for-profit or exempt entities.

Threshold and measurement period: The $4 million gross receipts threshold includes total gross receipts from all activities, both within and outside Wisconsin, including sales of tangible and intangible property, services, interest, dividends, and all other business activities for the taxable year. The measurement is performed at the entity level. For unitary combined groups, the test is applied to each member separately (not the group as a whole).

Calculation method and rates:

• For C corporations and insurance companies, the surcharge is 3% of the gross Wisconsin franchise or income tax liability (after all nonrefundable credits), with a minimum surcharge of $25 and a maximum of $9,800 per entity.
• For S corporations, the surcharge is 0.2% of Wisconsin net income as computed for Wisconsin tax purposes (with the same $25 minimum and $9,800 maximum per entity).
• For partial-year filers, the minimum and maximum are prorated based on the number of months covered in the short-period return.

Filing and payment: The surcharge is reported and paid with the same return as the Wisconsin franchise or corporate income tax (Forms 4, 5, or 5S, as applicable). Proper documentation and computation must be retained for audit purposes.

Primary authority: The surcharge is imposed under Wis. Stat. §§ 77.93 and 77.94. Further definitions and computational guidance are in Wis. Admin. Code Tax 2.32 as well as official Department of Revenue FAQs.

Source: Wis. Stat. § 77.93; Wis. Stat. § 77.94; Wis. Admin. Code Tax 2.32; Wisconsin DOR Economic Development Surcharge FAQ

Direct answer: Wisconsin requires mandatory combined reporting for corporations that are members of a "unitary business" group under common ownership—defined as more than 50% (by voting power or value) direct or indirect ownership—unless specifically exempted under statute. Single-company returns are not permitted for those who meet these unitary and ownership criteria, and combined filing is generally not elective.

Statutory structure and requirements:

• Mandatory for unitary groups: Wis. Stat. § 71.255(2)(a) requires every corporation engaged in a unitary business with one or more other corporations, where commonly controlled, to be included in a combined return. "Unitary business" is defined in Wis. Stat. § 71.255(1)(n); key characteristics include functional integration, centralized management, and economies of scale among group members.
• Ownership threshold: The "commonly controlled group" is defined in Wis. Stat. § 71.255(1)(c) as corporations with more than 50% of voting stock or value, owned directly or indirectly, by a common owner or owners. The statute is explicit regarding direct and indirect ownership but does not use the phrase "constructive ownership" or include detailed attribution rules found in federal law.
• Exclusions: Certain entities are mandatorily excluded from the combined group. These include insurance companies subject to Wisconsin premium tax under Wis. Stat. Ch. 76 (per Wis. Stat. § 71.255(1)(b)), S corporations, real estate investment trusts meeting federal qualifications, and entities specifically exempt under sections 71.26(1) or 71.45(1). Each exclusion is detailed in Wis. Stat. § 71.255(1)(b), (4).
• Election for broader inclusion: While combined reporting is mandatory for corporations meeting the unitary business and ownership requirements, there is a statutory election for a "controlled group" to expand the combined group to all entities under common control (including those outside the statutory unitary business) via a combined return election under Wis. Stat. § 71.255(2m). This election, once made, binds all group members to the broader "commonly controlled group" definition for the duration specified by the Department of Revenue.

Source support:

• Statutory imposition and scope: Wis. Stat. § 71.255(2)(a) (mandatory combined reporting for unitary groups)
• Ownership threshold: Wis. Stat. § 71.255(1)(c) (more than 50% ownership by vote or value; indirect ownership mechanisms named, but not federal-style constructive ownership rules)
• Exclusions and election: Wis. Stat. § 71.255(1)(b) (insurance and exempt entities), (4) (S corporations, REITs), (2m) (election to include all commonly controlled entities)

Source: Wis. Stat. § 71.255

Most corporations subject to Wisconsin franchise or income tax must make estimated tax payments if their net tax liability for the year is more than $500. Estimated payments are normally due in four equal installments, each on the 15th day of the 4th, 6th, 9th, and 12th months of the taxable year. For fiscal years beginning in April, the first two payments may be combined and paid on the second due date (see 2026 Corp-ES Instructions, p. 6).

Safe harbor thresholds to avoid underpayment interest:

• For corporations with net income under $250,000, no interest will be charged if the total paid is at least the lesser of (a) 90% of the current year’s tax or (b) 100% of the prior year’s tax liability (Wis. Stat. § 71.29(3), 2026 Corp-ES Instructions, p. 2-3).
• For corporations with net income of $250,000 or more, estimates must be at least 90% of the current year’s tax to avoid interest. The prior-year safe harbor is not available to “large corporations.”

First-year and short-period taxpayers:

• New corporations must compute payments as if the first taxable year were a full 12-month period. If the first return is for fewer than 12 months, estimated payments are annualized according to 2026 Corp-ES Instructions, p. 5.

Annualization option:

• Corporations whose income is not received evenly throughout the year may elect to annualize their estimated liability using annualization worksheets (2026 Corp-ES Instructions, p. 5-7). This may help avoid or reduce underpayment interest.

Special notes:

• S corporations are not required to make estimated tax payments (2026 Corp-ES Instructions, p. 2).
• Insurance companies are subject to separate estimated tax rules.
• Consolidated filers must make group estimates if filing a single consolidated return; see 2026 Corp-ES Instructions, p. 2 and 12.
• Underpayment of estimated tax results in nondeductible interest, calculated from the payment due date to the earlier of the return due date or actual payment (Wis. Stat. § 71.29(5)). Example calculations and detailed penalty formulas are provided in the Corp-ES instructions, p. 10-12.

Source: Wis. Stat. § 71.29; 2026 Wisconsin Corp-ES Instructions

Direct answer: For tax years beginning on or after January 1, 2023, Wisconsin conforms to the Internal Revenue Code (IRC) as amended through December 31, 2022, with specific exceptions for bonus depreciation, IRC §163(j) interest limitation, and U.S. international income provisions such as GILTI, Subpart F, and the §965 transition tax.

Why: • Conformity date:

• Wisconsin historically used the IRC as it existed on December 31, 2020.
• 2023 Wisconsin Act 36 updated the conformity date to December 31, 2022, for taxable years beginning on or after January 1, 2023.

(Source: Wis. Stat. § 71.22(4)(m); 2023 Wis. Act 36)

• Bonus depreciation:

• Wisconsin does not conform to federal bonus depreciation under IRC §168(k).
• Instead, depreciation must be calculated using federal law as it stood on January 1, 2014.
• Taxpayers must add back federal bonus depreciation and compute state depreciation under pre-bonus rules.

(Source: 2023 Wisconsin Form 6 Instructions)

• IRC §163(j) business interest limitation:

• Wisconsin does not adopt the post-TCJA federal limitation on business interest under §163(j).
• The state continues to follow pre‑TCJA federal rules, with no disallowance or carryforward for excess interest.

(Source: Wis. Stat. § 71.26(2)(b))

• GILTI, FDII, and Subpart F income:

• Wisconsin excludes GILTI (IRC §951A) and FDII (IRC §250) inclusions from its taxable base.
• For Subpart F income (IRC §951), Wisconsin allows a subtraction for Subpart F inclusions that were included federally but are not otherwise deductible.

(Sources: Wis. Stat. § 71.26(2)(b)14; § 71.26(3)(u); 2023 Form 6 Instructions)

• Section 965 transition tax:

• Income included federally under IRC §965 (transition/toll tax) is subtracted from Wisconsin taxable income.

(Sources: Wis. Stat. § 71.26(3)(vm); 2023 Form 6 Instructions)

Source support:

• Conformity date and bonus depreciation:

Wisconsin Statutes § 71.22(4)(m); 2023 Wisconsin Act 36; 2023 Wisconsin Form 6 Instructions

• Interest limitation and international provisions:

Wisconsin Statutes § 71.26 subsections (2)(b), (2)(b)14, (3)(u), (3)(vm), (3)(vo), (3)(vp); 2023 Wisconsin Form 6 Instructions

Source: Wis. Stat. § 71.22(4)(m), 2023 Wisconsin Act 36, 2023 Wisconsin Form 6 Instructions.

Caution / review status: Not yet human confirmed. This summary is accurate as of 2026‑06‑16, based on Wisconsin statutory and DOR guidance. Users should verify the current conformity date and decoupling items before applying to specific year filings.

Wisconsin recognizes the federal immunity provided by Public Law 86-272 (15 U.S.C. §§ 381–384) for out-of-state corporations whose only Wisconsin activity is the solicitation of sales of tangible personal property, with orders approved and shipped from outside the state. Under Wis. Admin. Code Tax 2.82, Wisconsin strictly applies P.L. 86-272 protection: a foreign corporation that engages in any activity in Wisconsin exceeding solicitation may lose immunity and be subject to corporate franchise/income tax.

However, as of June 2026, Wisconsin has not issued official administrative guidance or bulletins adopting or rejecting the Multistate Tax Commission’s (MTC) 2021 revised guidance regarding P.L. 86-272 and internet-based activities. Unlike a few other states, the Wisconsin Department of Revenue has not published determinations—either by regulation, notice, or income tax publications—taking a public position on whether common digital activities by remote sellers (e.g., interactive website chat functions, post-sale support portals, or placement of cookies for data collection) exceed the "solicitation" protections of P.L. 86-272. The Department’s published rules (Tax 2.82) predate the MTC’s 2021 update and do not address these scenarios.

Practical implications: In the absence of Wisconsin-specific pronouncements, practitioners must rely on the plain language of Tax 2.82 and federal law. Whether a given internet activity destroys immunity is fact-dependent. The Wisconsin DOR may assert nexus based on non-solicitation activities, but there is no published indication of enforcement positions specific to post-sale internet activities, cookie drops, or helpdesk chats. Taxpayers concerned about specific web-based practices should seek a private letter ruling or monitor the DOR for updated guidance post-MTC.

Source: Wis. Admin. Code Tax 2.82