Most states levy an income tax on their residents that is in addition to the federal income tax. Laws vary from state to state but in most states the state income tax is a tax on the annual earnings of individuals, corporations, trusts, limited liability companies, and other legal entities.

There are nine states that do not have a state income tax—including Alaska, Florida, Nevada, New Hampshire, South Dakota, Tennessee, Texas, Washington, and Wyoming. But New Hampshire levies a tax on capital gains and Washington state recently enacted a tax on extraordinary profits from the sale of financial assets over $250,000.

In Wisconsin, like most states, residents are subject to state income tax in addition to federal income tax. The state imposes an income tax on the annual earnings of individuals, corporations, trusts, limited liability companies, and other legal entities. The tax rates are progressive for individuals, meaning that the rate increases as income rises. Wisconsin's tax system includes multiple brackets with varying rates depending on the level of income. Corporations are also taxed at a flat rate on their income. It's important for residents and entities in Wisconsin to be aware of their tax obligations and to file their state income tax returns annually by the due date, typically April 15th, unless an extension is filed. Unlike the states mentioned that do not have a state income tax or only tax certain types of income, Wisconsin has a more comprehensive state income tax structure.