noun
tonnage dues; tonnage tax
A tax levied on ships based on their tonnage, typically when entering a port.
外国船が入港する際にはトン税が課される。
Tonnage dues are imposed when foreign ships enter the port.
関税 is a general customs duty on goods, while トン税 is specifically a charge based on a ship's tonnage.
Compound of トン (ton) and 税 (tax). The kanji spelling 噸税 uses the ateji 噸 for 'ton'.