The term Nenshaku means the right to confer a court rank on a person that was granted to chiten no kimi (the Retired Emperor in power) and sangu (the Three Empresses : Great Empress Dowager, Empress Dowager and Empress) in Japan's ancient/early medieval period. Each of the chiten and sangu was given every year the right to confer a court rank on one person and allowed to confer the Jugoi (Junior Fifth Rank) on one of the applicants in return for a payment of joryo (a fee for attaining a court rank). This system started in the early Heian period and later, the privilege of nenshaku was also granted to nyoin (close female relatives of the Emperor or a woman of comparative standing) and jugo (honorable rank next to the three empresses).
This system was originally the sale of court rank, like the system of eishaku under which temples/shrines and guji (chief of those who serves shrine) were conferred court ranks in return for a payment of joryo. In the end of the Heian period and the Kamakura period however, shojo (promotion) (kakai (promotion)) using the nenshaku system became popular.