VAT is an indirect tax in which the tax is levied by a person other than the person who actually bears the costs of the tax (i.e. the seller and not the consumer). In order to avoid double taxation of final consumption, exports (by definition consumed abroad) are generally not subject to VAT and VAT levied under these conditions is generally recoverable. The increasingly used rates have the important advantage of adjusting the tax burden according to the amount that the consumer spends on the goods taxed. They thus avoid serious discrimination of certain rates with regard to cheap varieties of products. The main difficulty in imposing value, especially with regard to customs duties, is to obtain a satisfactory value.