Cho was at first a kind of document used in kushikiryo (according to he Ritsuryo system) when a low- or medium-ranked government official higher than sakan submitted a petition to a higher government official, it was later used as texts exchanged between the office of Monastic affairs or Buddhist temples and a government official.
牒は、公式令(律令制)においては主典以上の官人が官司に対して上申する際に用いられる文書形式であったが、後に僧綱や寺社と官司とが文書の遣り取りを行う際にも用いられるようになった。