31 jan 521 ano antes da era comum - Taxes and coins

Descrição:

Darius replaced Cyrus and Cambysses's tax system with a proper one.

Before, people were required to gift the Emperor annually with silver, horses, and slaves, which was nice for the Emperor but didn't really help in paying armies and building structures.

So what Darius did was he created an actual currency, a standardized coin, and required that everyone paid him with those rather than gifts. The money was used for actual public stuff.