Registration Requirements in Wisconsin 

Most businesses that operate in Wisconsin will need to register with the Wisconsin Department of Revenue. Businesses may also have to register with other state agencies. The State of Wisconsin has a One Stop Business Portal to assist the registration process, found here

S-Corporation Income Tax

Wisconsin recognizes the federal S-election, and Wisconsin S corporations are not required to pay tax to the state. However, individual S corporation shareholders will owe tax on their share of the corporation’s income.

S corporations are required to file Form 5S.

LLC/Partnership Income Tax

LLCs and partnerships are not required to pay income tax to Wisconsin. Instead, income from the business is distributed to individual LLC members or partners, who then pay Wisconsin income tax on that amount with their personal return.

Partnerships are required to file Form 3

Composite Tax

Wisconsin allows s corporations and partnerships with qualified nonresident shareholders/partners to file composite tax returns on their behalf. Composite returns are not required. S corporations use Form 1CNS and partnerships use Form 1CNP.

Individual Income Tax

Individual income tax rates vary from 4.00% to 7.65%, depending upon filing status and income. Tax brackets are as follows: 

Individual income tax is filed on Form 1.

Due Dates

S corporations and partnerships must file their returns by the 15th day of the 4th month following the close of the tax year. For calendar year filers, the due date is March 15th. 

Individual income tax returns are due on April 15th. 

Estimated Payments

If a business or individual can reasonably expect to owe more than $500 at the end of the tax year, they must make quarterly estimated payments. 

Filing an Extension 

Wisconsin recognizes the federal extension for s corporations, partnerships, and individuals. If a federal extension was requested, you should include a copy of the request when you file your Wisconsin return.  

Penalties 

Wisconsin returns not filed in a timely manner may be subject to a $50 late filing fee, 1.5% interest and a negligence penalty of 5% per month up to 25% of the balance due. 

Additional Information

Wisconsin applies an “Economic Development Surcharge” for businesses that have at least $4 million in gross receipts. The surcharge is the greater of:

2% of net business income attributable to Wisconsin; or
$25.
The due date for the surcharge is the 15th day of the third month after year-end.

If your business was formed or is located in another state, but generates income in Wisconsin, it may be subject to Wisconsin taxes. The rules for taxation of multistate businesses, including what constitutes nexus with a state for the purpose of various taxes, are complicated. If you run such a business, you should consult with a tax professional.

Wisconsin Department of Revenue: 

https://www.revenue.wi.gov/pages/home.aspx 

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