Ad valorem tax

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.

A sales tax is a consumption tax charged at the point of purchase for certain goods and services. The tax is usually set as a percentage by the government charging the tax. There is usually a list of exemptions. The tax can be included in the price (tax-inclusive) or added at the point of sale (tax-exclusive).

Ideally, a sales tax is fair, has a high compliance rate, is difficult to avoid, is charged every time an item is sold retail, and is simple to calculate and simple to collect. A conventional or retail sales tax attempts to achieve this by charging the tax only on the final end user, unlike a gross receipts tax levied on the intermediate business which purchases materials for production or ordinary operating expenses prior to delivering a service or product to the marketplace. This prevents so-called tax "cascading" or "pyramiding," in which an item is taxed more than once as it makes its way from production to final retail sale. There are several types of sales taxes: seller or vendor taxes, consumer excise taxes, retail transaction taxes, or value-added taxes.

A value-added tax (VAT), or goods and services tax (GST), is tax on exchanges. It is levied on the added value that results from each exchange. It differs from a sales tax because a sales tax is levied on the total value of the exchange. For this reason, a VAT is neutral with respect to the number of passages that there are between the producer and the final consumer. A VAT is an indirect tax, in that the tax is collected from someone other than the person who actually bears the cost of the tax (namely the seller rather than the consumer). To avoid double taxation on final consumption, exports (which by definition are consumed abroad) are usually not subject to VAT and VAT charged under such circumstances is usually refundable.

...
Wikipedia