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
Laws Imposing Taxes - Laws of Credit
In the system of taxation and of credit also efforts were made with greater energy at this period than at any before or subsequent to it to remedy the evils of the national economy, so far as legal measures could do so. The duty levied in 397 of five per cent on the value of slaves that were to be manumitted was--irrespective of the fact that it imposed a check on the undesirable multiplication of freedmen--the first tax in Rome that was really laid upon the rich. In like manner efforts were made to remedy the system of credit.
The usury laws, which the Twelve Tables had established,(9) were renewed and gradually rendered more stringent, so that the maximum of interest was successively lowered from 10 per cent (enforced in 397) to 5 per cent (in 407) for the year of twelve months, and at length (412) the taking of interest was altogether forbidden. The latter foolish law remained formally in force, but, of course, it was practically inoperative; the standard rate of interest afterwards usual, viz. 1 per cent per month, or 12 per cent for the civil common year--which, according to the value of money in antiquity, was probably at that time nearly the same as, according to its modern value, a rate of 5 or 6 per cent--must have been already about this period established as the maximum of appropriate interest.
9. Cf. II. II. Legislation of the Twelve Tables
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