There are two main methods of calculating VAT:
1. Credit-invoice method, sales transactions are taxed, with the customer informed of the VAT on the transaction, and businesses may receive a credit for VAT paid on input materials and services. The credit-invoice method is the most widely employed method, used by all national VATs except for Japan.
2. Subtraction method, at the end of a reporting period, a business calculates the value of all taxable sales then subtracts the sum of all taxable purchases and the VAT rate is applied to the difference. The subtraction method VAT is currently only used by Japan, although subtraction method VATs, often using the name "flat tax", have been part of many recent tax reform proposals by US politicians.
With both methods, there are exceptions in the calculation method for certain goods and transactions, created for either pragmatic collection reasons or to counter tax fraud and avoidance.