Although Darius established a standard gold coinage, and some payments were made in silver, much of the system operated by payments in kind. These were assessed,
and the assessment was based on the value of the goods received. The system was not a simple one, and the assessment was not always made in the same way.

The system was not always successful. The Persians were defeated by Alexander the Great in 333 BC, and the Macedonians took over the Persian