W. Va. Code § 7-27-31

A vendor selling tangible personal property or custom software or furnishing a service in a county that imposes a county transportation sales tax pursuant to this article shall for the privilege of doing business in the county collect the county transportation sales tax from the purchaser at the same time and in the same manner that the tax imposed by article fifteen, chapter eleven of this code, is collected from the customer. All sales of tangible personal property and custom software made in the county and all services furnished in the county are presumed to be subject to the county transportation sales tax unless an exemption or exception applies.