official institution of land distribution and tax collection in traditional China and Japan. The system originated in China in 485 CE by order of the emperor Xiaowendi of the Bei (Northern) Wei dynasty (386–534/535 CE). It provided for the assignment of agricultural lands to all adult peasants and thereby slowed the accumulation of lands by wealthy families. During the Bei Wei a man and wife were entitled to a total of about 140 mou (about 20 acres 【8 hectares】), of which a small part was irrevocably held by them; the remaining land was returned to the government upon age 70 or their deaths. During the Tang (Tang dynasty) period (618–907) the system was enforced throughout the country and became the most important fiscal institution of the central government. Each adult between the ages of 21 and 59 was given 80 mou (about 12 acres 【5 hectares】), of which one-fourth was permanently owned. A fixed amount of produce from the land was subsequently paid as tax in kind to the government. The greatest allotment of land was limited to 100 qing (10,000 mou) and was reserved only for the most highly ranked of the great families. The system gradually declined with the swift growth in population (early 8th century), as most peasants increasingly inherited less than 100 mou, and most landholdings came to be permanently held and not redistributed. Most of the better lands were then acquired by wealthy families, and the original per capita tax system declined rapidly. After the collapse of the system during the Xuanzong emperor's reign (712–756), it was not reinstituted except on a local scale.

The equal-field system was applied in Japan as a result of the Taika era reforms (646 CE) but declined in the Nara period (710–784), when both nobles and monasteries were given additional land allotments and tax-free status.