A Migyosho (or Mikyosho) was a form of ancient document issued by a Keishi (household superintendant) with a court rank of Jusanmi (Junior Third Rank) or higher used for conveying the intentions of their masters from the late Heian period to the Muromachi period. Documents with the same style issued by Keishi or Kaboku (servant) of nobilities with a rank lower than Jusanmi or Shugodaimyo (military governor) used for conveying their masters' intention was called hosho.
As a matter of formality, Migyosho were written in the same style as Rinji (Imperial order), Inzen (decree from the Retired Emperor) and Ryoji (orders issued by princes, empresses etc.). Although they were written in the style of a private letter, they were customarily written by a Keishi since it was common for those with high rank to have their close aides write on their behalf. As a result, the sender was also a Keishi and the master would add their sodeban (signature) when necessary.
At the end of one of these documents, a phrase emphasizing that a letter was written in accordance with the intention of a master was added, such as, 'The statements above were made by him/her.'
As a Migyosho was a notice or emergency order, its status as a document was inferior to a Kudashibumi (a document issued by a superior or office), which was an official document and effective indefinitely as a court ruling, license proof, etc.
The oldest Migyosho still in existence was issued by FUJIWARA no Tadazane on November 25, 1116.
Migyosho issued by the head of the Sekke (the top five Fujiwara families whose members were eligible for the positions of Sessho and Kanpaku) were called 'Denka Migyosho.'
Minamoto no Yoritomo established the base of bukeyo monjo (a samurai-style document) which consisted of three kinds of documents; these were the Kudashibumi, Gejijo (a document issued by a vassal of the Shogun for conveying Shogun orders) and Migyosho. Documents issued by Yoritomo prior to his promotion to Junii (Junior Second Rank) on June 4, 1185, however, were called hosho. After the death of Yoritomo, the Kamakura bakufu (Japanese feudal government headed by a shogun) used Migyosho as the method for passing on information of official intentions. The frequency in which Migyosho were used gradually increased as the use of Kudashibumi and Gejijo decreased.
During the Muromachi period, Migyosho drove out Kudashibumi as well as Gejijo and became the highest ranking document style among documents issued by the bakufu. However, as Gonaisho (an official document) adopted the style of Jikijo (a private document) and came to be more wildey used, Migyosho gradually fell into disuse.