The client states recognized as fully sovereign--such as the kingdoms of Numidia and Cappadocia, the allied states (-civitates foederatae-) of Rhodes, Messana, Tauromenium, Massilia, Gades--were legally exempt from taxation, and merely bound by their treaties to support the Roman republic in times of war by regularly furnishing a fixed number of ships or men at their own expense, and, as a matter of course in case of need, by rendering extraordinary aid of any kind.
Taxes The rest of the provincial territory on the other hand, even including the free cities, was throughout liable to taxation; the only exceptions were the cities invested with the Roman franchise, such as Narbo, and the communities on which immunity from taxation was specially conferred (-civitates immunes-), such as Centuripa in Sicily.

The direct taxes consisted partly--as in Sicily and Sardinia--of a title to the tenth( 8) of the sheaves and other field produce as of grapes and olives, or, if the land lay in pasture, to a corresponding -scriptura-; partly--as in Macedonia, Achaia, Cyrene, the greater part of Africa, the two Spains, and by Sulla's arrangements also in Asia--of a fixed sum of money to be paid annually by each community to Rome (-stipendium-, -tributum-).
This amounted, e.g.for all Macedonia, to 600,000 -denarii- (24,000 pounds), for the small island of Gyaros near Andros to 150 -denarii- (6 pounds, 10 shillings), and was apparently on the whole low and less than the tax paid before the Roman rule.

Those ground-tenths and pasture-moneys the state farmed out to private contractors on condition of their paying fixed quantities of grain or fixed sums of money; with respect to the latter money-payments the state drew upon the respective communities, and left it to these to assess the amount, according to the general principles laid down by the Roman government, on the persons liable, and to collect it from them.( 9) Customs 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.