Portoria was the Roman Empire’s general customs duty on goods crossing provincial and other fiscal boundaries.
The term referred to customs charges collected at ports, roads, bridges, and frontier stations. Rates and administrative practices varied over time and by location, so portoria was a broad category rather than one permanently fixed empire-wide percentage.
Customs revenue was an important part of Roman public finance. Officials or contractors could collect duties when merchandise entered a territory, and disputes could arise over classification, valuation, and whether goods were for local use or onward trade.
Portoria should not be confused with the centesima rerum venalium, a separate Roman sales tax often associated with auctions and sales, or with the chrysargyron, a later tax on commercial activity. Those were distinct levies with different bases.