Kantojo (官途状) is a letter which was used after the Muromachi period which stated, that a vassal who distinguished himself in a battle was allowed by his lord to use a specific government post as his private name.
官途状（かんとじょう）とは、室町時代以降、主君が武功を挙げた家臣に対して特定の官職を私称することを許した書状のことである。