The term "Gonkan" means official court posts that were created beyond the prefixed number of personnel.
It means 'supernumerary officials.'
Such posts were often created in the Heian period. Incidentally, ingaikan (supernumerary officials) were appointed in the Nara period.
Many court nobles were appointed to gonkan in the Heian period and the posts of gonkan were always occupied by someone. The following situation existed behind the above. At that time, there was a custom where family heads or sons of prestigious families, including the Fujiwara family, were automatically given official ranks, regardless of their ability, when they reached a certain age. On the other hand, the number of government posts was predetermined. Under these conditions, there was a need to create gonkan in order to give them posts.
When we compare gonkan and regular posts, taking the example of Dainagon (chief council of state) and Gon Dainagon (provisional chief council of state), there were cases where both had the same authority as well as cases where one had authority while the other was a nominal post. A nominal title of gonkan was sometimes used in order to demote one's political rival, such as the case of SUGAWARA no Michizane. He lost his position through a conspiracy perpetuated by the Fujiwara clan and was appointed to 'Gon no sochi' (provisional governor-general) of Dazaifu (local government office in Kyushu region), the gonkan of Dazai no sochi (the head of Dazaifu). Though the post itself was a high-rank, he was actually banished to Kyushu where Dazaifu was located.
After the Northern and Southern courts period, according to "Kanshoku konan" written by Tomokiyo TAKADA, only gonkan existed, instead of regular ones, in the case of Dainagon and Chunagon (vice-council of state).
Gon Chunagon (provisional vice-council of state)
Gon no kami (provisional provincial governor)
Gon no kokushi (provisional provincial governor)
Gon no hyoe (provisional vice-minister of Imperial Guard Division)
Gon no sojo (provisional lower priest in the highest position)
Gonsuke: kitchen workers of merchant's family
Or one of official posts in the Meiji era.
It is equivalent to soninkan (the posts to which persons are appointed by the Emperor based on the recommendation of the prime minister)