vicesima libertatis
From LSJ
ἔκστασίς τίς ἐστιν ἐν τῇ γενέσει τὸ παρὰ φύσιν τοῦ κατὰ φύσιν → what is contrary to nature is any developmental aberration from what is in accord with nature (Aristotle, On the Heavens 286a19)
Wikipedia EN
The vicesima libertatis, also known as the vicesima manumissionum was an ancient Republican Roman tax on freed slaves. If the master freed the slave the government would tax the master for 5% of the slaves value. If the slave freed themselves they would be taxed. Another possibility is that the tax was for registering a slave as free, not for freeing them in the first place. It was established in 357 BCE by the Consul Gnaeus Manlius. There is no archaeological evidence for this tax in all provinces except for Italy before the Severan dynasty.
