Legal Definitions - tonnage duty

A tonnage duty is a tax or fee imposed by a government on commercial vessels, typically calculated based on the ship's carrying capacity or internal volume, often referred to as its "tonnage." This duty is usually collected when a ship enters or leaves a port, or when it navigates certain waterways, and contributes to the funding of port operations, navigational aids, or other maritime infrastructure.

Here are some examples illustrating tonnage duty:

• International Cargo Ship: A large container ship, registered in Panama, arrives at the Port of Los Angeles after transporting goods across the Pacific Ocean. Before the ship is permitted to dock and unload its vast cargo, the U.S. Customs and Border Protection agency assesses a tonnage duty. This fee is calculated based on the ship's net tonnage (its cargo-carrying capacity) and contributes to the maintenance of the harbor, navigational services, and other port infrastructure.

• Cruise Liner in the Caribbean: A luxury cruise ship embarks on a week-long journey from Florida, making stops at various island nations. As the cruise ship enters the territorial waters and docks at the port of each sovereign island, the local port authority levies a tonnage duty. This charge, often based on the ship's gross tonnage (its total internal volume), helps fund the upkeep of the port facilities that accommodate large passenger vessels and supports the local maritime economy.

• Domestic Bulk Carrier: A bulk carrier, owned by a domestic shipping company, transports iron ore from a mining port on the Great Lakes to a steel manufacturing port on the East Coast of the same country. Even though the voyage is entirely within national waters, the government imposes a tonnage duty on the vessel for its use of federally maintained waterways and port facilities. This duty, calculated on the ship's capacity, helps cover the costs associated with dredging channels and maintaining navigational aids along the shipping route.