How it works/Example: There are generally two types of tariffs. Ad valorem tariffs are calculated as a fixed percentage of the value of the imported good. When the international price of a good rises or falls, so does the tariff. A specific tariff is a fixed amount of money that does not vary with the price of the good.In some cases, both the ad valorem and specific tariffs are levied on the same product.hen the international price of a good rises or falls, so does the tariff. A specific tariff is a fixed amount of money that does not vary with the price of the good. In some cases, both the ad valorem and specific tariffs are levied on the same product.