An ad valorem tax (Latin for "according to value") is a tax whose amount is based on the value of a transaction or of property. It is typically imposed at the time of a transaction, as in the case of a sales tax or value-added tax (VAT). An ad valorem tax may also be imposed annually, as in the case of a real or personal property tax, or in connection with another significant event (e.g. inheritance tax, expatriation tax, or tariff). In some countries a stamp duty is imposed as an ad valorem tax.