The term "Yusoden" means rice fields on which denso (rice field tax) was imposed under the taxation system of Ritsuryo system (a system of centralized government based on the Ritsuryo Code).
The amount of denso was nitaba-niwa (two sheaves and two bunches) per a dan (about 992 ㎡)of rice field under Taiho Code and it was revised to hitotaba-gowa (one sheaves and five bunches) by Kakushiki (amendment of Ritsuryo Code) dated October 21, 706. It is said that the above revision was made only because of the change of the system of weighs and measures and the actual amount remained unchanged. Denso was delivered from Yusoden to kokuga (provincial government offices) from September (old calendar) to November (old calendar) every year when rice was harvested. In addition to denso, shozei (rice tax) and suiko (seed rice used for government loan system) were also imposed. On the other hand, rice fields which were exempted from denso were called fuyusoden (provided that rice fields which didn't belong either of the above two categories called yujishiden (such as joden, mushuden and shukoden on which jishi (land tax) was imposed instead of denso) also existed).
Though the distinction between yusoden and fuyusoden varied depending on the times, it is commonly understood that kubunden (rice fields given to each peasant), iden (rice fields given based on the court rank), kuden (rice fields given to those who did meritorious deeds for the state), shiden (rice fields given by the Emperor), kokuzoden (rice fields given to local officials), gunjishikiden (rice fields given to gunji (local magistrate) and konden (newly developed rice fields) were categorized as yosoden and shikiden (rice fields given to high-ranking officials), kugaiden, ekiden, kanden (imperial rice fields), jiden (rice fields associated with temples), shinden (rice fields associated with shrines) and unemeden were categorized as fuyusoden.
According to the decline of handensei (Ritsuryo land allotment system), taxation system of rice fields itself changed and eventually, yusoden and yujishiden were integrated into koden (rice fields administered directly by a ruler) and denso and jishi were integrated into sokoku. Although the standard amount of sokoku was santo (about fifty-four liters) (equivalent to six sheaves), the actual imposed amount was not constant. Under such situation, a new standard called Koden kanmotsu rippo (the law fixing the tax rate for koden) was introduced in the eleventh century.
Rice fields categorized as yusoden were imposed denso even though they were influential families' shoen (manor). In the tenth century, however, these influential families obtained fuyu no ken (the right of tax exemption) by Daijokanpu (official documents issued by Daijokan, Grand Council of State)/Minbushofu (official documents issued by Minbusho, Ministry of Popular Affaires) and converted their shoen into fuyusoden in effect. These shoen were called Kanshofu sho (shoen exempted from tax by Daijokanpu/Minbushofu). In order to cope with such a situation, Shoen seirirei (decree restricting the expansion of shoen) was issued.