Legal Definitions - duty of tonnage

Duty of Tonnage

A duty of tonnage refers to a tax or charge imposed on a ship, calculated based on its carrying capacity or volume (its "tonnage"). This type of duty is typically levied for the privilege of entering, using, or departing from a port, harbor, or other navigable waterway. In many legal systems, particularly in the United States, the power to impose such duties is reserved exclusively for the federal government, preventing individual states from levying their own tonnage duties without federal consent.

• Example 1: A large container ship arrives at the Port of Seattle from South Korea, carrying thousands of tons of electronics and consumer goods.

  Explanation: The United States federal government might impose a tonnage duty on this vessel for the right to enter the port, dock, and unload its cargo. This duty would be calculated based on the ship's registered tonnage, contributing to the maintenance and security of the port and federal waterways. This illustrates a tonnage duty applied to international commercial shipping.

• Example 2: A company operates a fleet of barges transporting coal along the Ohio River, which borders several states.

  Explanation: If the state of Kentucky attempted to impose a fee on these barges based on their carrying capacity simply for navigating its portion of the river, this would likely be considered an unconstitutional duty of tonnage. The U.S. Constitution reserves the power to levy such duties to the federal government, preventing individual states from creating barriers to interstate commerce through ship-based taxes.

• Example 3: A major cruise line operates a luxury liner departing from the Port of Miami for a week-long Caribbean voyage with thousands of passengers.

  Explanation: The federal government could levy a tonnage duty on this cruise ship for its use of the port facilities and navigable channels. This duty would be calculated based on the ship's gross tonnage, contributing to the upkeep of the port infrastructure and maritime services, demonstrating that such duties apply to passenger vessels as well as cargo ships.