based on the market value of each property on a particular date, and most jurisdictions require redeterminations of value periodically. The tax is computed as the determined market value times an assessment ratio times the tax rate. Assessment ratios and tax rates vary widely among jurisdictions, and may vary by type of property within a jurisdiction. Where a property has recently been sold between unrelated sellers, such sale establishes fair market value. In other (i.e., most) cases, the value must be estimated. Common estimation techniques include comparable sales, depreciated cost, and an income approach. Property owners may also declare a value, which is subject to change by the tax assessor. Types of property taxed Property taxes are most commonly applied to real estate and business property. Real property generally includes all interests considered under that state's law to be ownership interests in land, buildings, and improvements. Ownership interests include ownership of title as well as certain other rights to property. Automobile and boat registration fees are a subset of this tax. Other nonbusiness goods are generally not subject to property tax, though Virginia maintains a unique personal property tax on all motor vehicles, including non-business vehicles. Assessment and collection The assessment process varies by state, and sometimes within a state. Each taxing jurisdiction determines values of property within the jurisdiction and then determines the amount of tax to assess based on the value of the property. Tax assessors for taxing jurisdictions are generally responsible for determining property values. The determination of values and calculation of tax is generally performed by an official referred to as a tax assessor. Property owners have rights in each jurisdiction to declare or contest the value so determined. Property values generally must be coordinated among jurisdictions, and such coordination is often performed by equalization. Once value is determined, the assessor typically notifies the last known property owner of the value determination. After values are settled, property tax bills or notices are sent to property owners. Payment times and terms vary widely. If a property owner fails to pay the tax, the taxing jurisdiction has various remedies for collection, in many cases including seizure and sale of the property. Property taxes constitute a lien on the property to which transfers are also subject. Mortgage companies often collect taxes from property owners and remit them on behalf of the owner. Customs duties The United States imposes tariffs