Gonaisho was an official document written in the style of a private letter that was issued by the Seii Taishogun (literally, great general who subdues the barbarians) of the Muromachi bakufu (Japanese feudal government headed by a shogun).
Although a Gonaisho was written in the style of a private letter with the sender's name written in the text, a kao (written seal mark) or shohan (signature/seal) was added to the document by the shogun himself. As a result, these documents were deemed as a kind of Migyosho (an official document informing people of a government decision), and even though it was more of a private order made by the shogun, it had the legal weight equivalent to an official bakufu order. It was initially issued mainly for the purpose of conveying the private business of the shogun. During the late Muromachi period, however, Gonaisho were increasingly issued in place of Migyosho issued by kanrei (shogunal deputy), and its nature became more of a quasi-official document used by the shogun to directly inform people of his intentions. The Edo bakufu inherited the Gonaisho as a document to inform people of the shogun's intentions. It was customary that, under normal circumstances, a Gonaisho was issued with an accompanying letter by an attendant who was a close aide to the shogun. There were two kinds of documentary forms, more specifically one which used respectful words in writing the name of the addressee and ending the letter, and a normal letter which did not use respectful words. Each type of form was separately used depending on the court rank and social status of the addressee.
Kojo, an official written appointment to the chief of the gozan (five great Zen temples in Kyoto) was issued either as a Migyosho or Gonaisho. It is also believed that orders given by Yoshiaki ASHIKAGA appealing to territorial lords to overthrow Nobunaga ODA were issued using Gonaisho.