For example, if an item costs $100 plus a VAT rate of 20 percent, the VAT calculation is $100 x 0.20 = $20, as shown by HM Revenue & Customs. The total cost of the item, including both the base price and the VAT, is found by adding the two together. For an item that costs $100 with a 20 percent VAT, the final price is calculated as $100 + $20 = $120.

To find the VAT from an item that has a total cost of $105, including a VAT taxed at a rate of 5 percent, the proper calculation is $105/1.05 = $100 to find the value of the item. From there, the VAT can be found by subtraction, as in the formula $105 - $100 = $5. When the VAT is included in the price, the price is considered VAT-inclusive. When VAT is not included, the price is VAT-exclusive, according to HM Revenue & Customs.