Roman finance

For centuries the monetary affairs of the Roman Republic had rested in the hands of the Senate. These elite liked to present themselves as steady and fiscally conservative, but as the 19th-century historian of Rome Wilhelm Ihne remarked:

The aerarium (state treasury) was supervised by members of the government rising in power and prestige, the Quaestors, Praetors, and eventually the Prefects. With the dawn of the Roman Empire, a major change took place, as the emperors assumed the reins of financial control. Augustus adopted a system that was, on the surface, fair to the Senate. Just as the world was divided in provinces designated as imperial or senatorial, so was the treasury. All tribute brought in from senatorially controlled provinces was given to the aerarium, while that of the imperial territories went to the treasury of the emperor, the fiscus.

Initially, this process of distribution seemed to work, although the legal technicality did not disguise the supremacy of the emperor or his often used right to transfer funds back and forth regularly from the aerarium to the fiscus. The fiscus actually took shape after the reign of Augustus and Tiberius. It began as a private fund (fiscus meaning purse or basket) but grew to include all imperial monies, not only the private estates but also all public lands and finances under the imperial eye.

The property of the rulers grew to such an extent that changes had to be made starting sometime in the 3rd century, most certainly under Septimius Severus. Henceforth the imperial treasury was divided. The fiscus was retained to handle actual government revenue, while a patrimonium was created to hold the private fortune, the inheritance of the royal house. There is a considerable question as to the exact nature of this evaluation, involving possibly a res privata so common in the Late Empire.

...
Wikipedia