How Do You Work Out The VAT Value Of An Item Purchased?

It rather depends what country you are in, and what rate the VAT, or value added tax is charged at, for example in some countries like Switzerland it is charged at 7% and in others like Italy it is charged at 20% so, when you know what the rate is, then work it out like this, it is rather simple really.
For example let us say the goods you bought where 100 Euros then the vat charged on that would be 20% which is 20 Euro really, and that you would have to pay at the time of purchase
People who have their own companies, are registered as vat
vendors, and they charge vat on the services or goods they sell, and then they pay it over to the government.

V.A.T, or Value Added Tax is rated in the UK on exchanges between vendor/service and consumer at 17.5% of the cost of the item or service. Unlike sales tax, VAT is collected directly from the vendor. If for instances, I was going to buy a box of toys, it is likely that the VAT has already been added to the price. However, when I pay for a service, such as a designer to design a flier or postcard to advertise my business, I should expect to pay VAT on top of the quoted price.

VAT was invented by a French economist (oh thanks) and was brought into use in 1954.

The rates in each country differ quite amazingly, in the UK it is 17.5%, whereas in Sweden it is as high as 25% and in Luxembourg as low as 15%. The lucky Japanese only pay 5%.