The nengu came from kanmotsu, eventually denso (rice field tax), and became central items of taxation in the land tax system for shoens and the item of taxation that were paid to high grade lords of the manor by local low grade lords of the manor (kaihatsu-ryoshu (local notables who actually developed the land) or shokan (an officer governing shoen (manor))).
年貢は、官物、ひいては田租に由来しており、荘園租税体系の中心に位置する税目であり、現地の下級荘園領主（開発領主や荘官など）が上級領主へ納入すべき税目であった。