a commercial vessel at a port.
during which passengers embark or disembark the vessel in the United States. Such term shall not include any voyage on any vessel owned or operated by the United States, a State, or any agency or subdivision thereof.
Taxable gross weight shall be determined under regulations prescribed by the Secretary (which regulations may include formulas or other methods for determining the taxable gross weight of vehicles by classes, specifications, or otherwise).
then the collection of the tax imposed by section 4481 with respect to the use of such vehicle shall be suspended during the taxable period.
then no tax shall be imposed by section 4481 on the use of such vehicle for the taxable period.
the amount of such tax shall be credited or refunded (without interest) to the person who paid such tax.