Overwriting - Overwriting

...After the abolition of the Sankan system in July 789 (Enryaku 8), the Ritsuryo system of kasho also declined.
[middle ages]
From the Kamakura period onwards in the Middle Ages, it was often erroneously written as "Kasho." Originally it was a permit to pass through a checkpoint, but in the Kamakura period, it referred to documents issued by the shogunate requesting the convenience of people and horses at post stations on the Tokaido road and other roads, as well as exemptions from tolls and other charges at checkpoints in the Middle Ages that had evolved into economic checkpoints for the purpose of collecting tolls.

*Some of the terminology explanations that mention "kasho" are listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…789年(延暦8)7月の三関（さんかん）停廃後は律令制的な過所制度も衰退した。【館野 和己】
［中世］
　鎌倉時代以降中世においては〈過書〉と誤って書かれることが多い。もともとは関所通行の許可証であったが，鎌倉時代になると，幕府より東海道などの宿駅で人馬の便宜をはかることを要請して発給された文書や，通行税徴収のための経済的関所へと変化した中世の関所における関銭等の免除状をさしていう。…

※「過書」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報