According to Kushiki-ryo (law on state documentary forms in the Yoro Code) (Ritsuryo law), there was a prescribed format of zi, 'the date, the name of the reporter, the main text and kinji (a closing sentence).'
公式令(律令法)によれば、「年月日　氏名辞、其事云々（本文）、謹辞」と書式が規定されている。