You searched for: “ad val
ad valorem; ad val., ad v., a/v; ad valorem tax (Latin terms)
Translation: "According to value or per unit of value; that is, divided by the price."

Many states and federal governments tax energy extraction in this manner.

It also refers to taxes: "In proportion to invoiced value of goods." A term used when imposing customs and stamp duty, the duty increasing according to the value of the transaction of goods involved. Pronounced in English as: ad vuh LOH ruhm.