A
per unit tax, or
specific tax, is a
tax that is defined as a fixed amount for each unit of a good or service sold, such as cents per kilogram. It is thus proportional to the particular quantity of a product sold, regardless of its price.
Excise taxes, for instance, fall into this tax category. By contrast, an
ad valorem tax is a charge based on a fixed percentage of the product value. Per unit taxes have administrative advantages when it is easy to measure quantities of the product or service being sold.