Shokudo (penalty charges) (贖銅)

Shokudo or zokudo is a penalty charge which was paid with copper (or money) to a government official in an amount that corresponds to the crime in exchange for imprisonment. There is an element of financial penalty or punishment by seizing assets to it. It was established in the age of Yoro ritsuryo code in Japan.

Summary
The five punishments (whipping, flogging, imprisonment, deportation, and capital punishment [Ritsuryo law]) stipulated in the ritsuryo system could be dispensed with by paying copper
Ten whippings were exchanged with a kin (600g) of copper, and 60 floggings were exchanged with 100 kin of copper (the number of flogging was 60 minimum and 100 maximum. In the Heian period, it was not only the mean to avoid imprisonment, but in more cases copper was demanded.

Example of shokudo
In 1147, TAIRA no Kiyomori was ordered by the Cloistered Emperor Toba to pay 30 kin of copper due to the Gion Brawling Incident.