Please note that Mommsen uses the AUC chronology (Ab Urbe Condita), i.e. from the founding of the City of Rome. You can use this reference table to have the B.C. dates
From: The History of Rome, by Theodor Mommsen
Translated with the sanction of the author by William Purdie Dickson
The indirect taxes consisted--apart from the subordinate moneys levied from roads, bridges, and canals--mainly of customs-duties. The customs-duties of antiquity were, if not exclusively, at any rate principally port-dues, less frequently frontier-dues, on imports and exports destined for sale, and were levied by each community in its ports and its territory at discretion.
The Romans recognized this principle generally, in so far as their original customs-domain did not extend farther than the range of the Roman franchise and the limit of the customs was by no means coincident with the limits of the empire, so that a general imperial tariff was unknown: it was only by means of state-treaty that a total exemption from customs-dues in the client communities was secured for the Roman state, and in various cases at least favourable term for the Roman burgess.
But in those districts, which had not been admitted to alliance with Rome but were in the condition of subjects proper and had not acquired immunity, the customs fell as a matter of course to the proper sovereign, that is, to the Roman community; and in consequence of this several larger regions within the empire were constituted as separate Roman customs-districts, in which the several communities allied or privileged with immunity were marked off as exempt from Roman customs.
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Reference address : https://www.ellopos.net/elpenor/rome/4-11-commonwealth-economy.asp?pg=10