It is considered that the original kubunden system began to be formed around the Taika Reforms, or in the middle era of the seventh century, and was established towards the end of seventh century when the ritsuryo system was formed.
口分田の祖型は、7世紀中葉の大化の改新頃に始まり、7世紀終盤の律令形成期に口分田制度が確立したと考えられている。