Most local governments in the United States impose a property tax, also known as a millage rate, as a principal source of revenue. This tax may be imposed on real estate or personal property. The tax is nearly always computed as the fair market value of the property times an assessment ratio times a tax rate, and is generally an obligation of the owner of the property. Values are determined by local officials, and may be disputed by property owners. For the taxing authority, one advantage of the property tax over the sales tax or income tax is that the revenue always equals the tax levy, unlike the other taxes. The property tax typically produces the required revenue for municipalities' tax levies. A disadvantage to the taxpayer is that the tax liability is fixed, while the taxpayer's inco