Impost

Part of speech: noun (n.)

1. That which is imposed or levied; a tax, tribute, or duty; especially, a duty or tax laid by goverment on goods imported into a country. Even the ship money . . . Johnson could not pronounce to have been an unconstitutional impost. Macaulay.

2. The top member of a pillar, pier, wall, etc., upon which the weight of an arch rests.

Synonyms: Tribute; excise; custom; duty; tax.