According to Kushiki-ryo (the law concerning official documentary forms) contained in "the Yoro Ritsuryo Code" under the Ritsuryo law system, there existed three kinds of Daijokan-so, namely Ronso, Soji and Binso.
『養老律令』公式令(律令法)によれば、論奏・奏事・便奏の3種類が存在した。