Up to the time of the second head priest Encho, the term Tendai-zasu was a private title used within the compound of Enryaku-ji Temple but, starting with the third head priest Ennin, it became an official post appointed by way of kanpu (official documents from the Dajokan or Grand Council of State) issued by the Dajokan, and which continued until 1871.
2世円澄までは延暦寺内の私称であったが、3世の円仁からは太政官が官符をもって任命する公的な役職となり、明治4年（1871年）まで続いた。