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.
Withholding tax is an amount withheld by the party making payment to another (payee) and paid to the taxation authorities. The amount the payer deducts may vary, depending on the nature of the product or service being paid for. The payee is assessed on the gross amount, and the tax to be withheld (the withholding tax) is computed in that assessment. The purpose of withholding tax is to counteract tax evasion and tax avoidance either by domestic or international taxpayers. In some jurisdictions, the purpose of deduction is also to facilitate or accelerate collection and no assumption about evasion is inferred.