Tax:

net amount (price before taxation)
tax value
Gross amount (including VAT) (price after taxation)

Taxation rate:

Value-Added-Tax calculations use different tax-rates, depending on:

• country - the rate is set individually for each country
• type of bussiness - the rate is dependent of taxed goods/services classification, many countries use reduced VAT rates for some particular groups of goods

The current rate for calculations is % (you can change it as you need)

The VAT rates in some countries (click to use):

• Czech Republic: 19%, 9%
• France: 19.6%, 5.5%, 2.1%
• Germany: 19%, 7%
• Ireland: 21%, 13.5%, 4.8%
• Poland: 23%, 8%, 5%
• Spain: 16%, 7%, 4%
• UK: 20%, 17.5%, 5%

You can find some other tax rates on wikipedia.