While most people automatically think of federal income tax when the subject of personal income tax is raised, not many people know that personal income tax was first introduced by the states. The state of Wisconsin has the dubious distinction of being the first to introduce a form of the personal income tax system in 1911. As of 2002, most states have some form of personal income tax. There are two basic methods to determine income tax, the graduated income tax and the flat rate income tax. Both methods require taxpayers to figure their taxable income.