The junshuifa 均税法 "equal-tax law", also called fangtian junshui fa 方田均稅法 "equal-tax law [based] on field compartments" or fangtian fa 方田法 "square-field method", was a project to adjust the registration of land and thus also the tax registers. It was first carried out in a test phase between 1043 and 1063 in Bozhou 毫州, Shouzhou 壽州, Ruzhou 汝州 and Caizhou 蔡州, but three times aborted. Only from 1072, when the reform-minded Wang Anshi 王安石 (1021-1086) was Counsellor-in-chief of the Song dynasty 宋 (960-1279), he realized the project, with the aim not only to see to it that taxes were more justly distributed on the shoulders of landowners and peasants, but also to increase the tax revenue in total. The new cadastres would unveil so-called "hidden land" (yintian 隱田).
For the reassessment (qingzhuang 清丈), fields were divided into "squares" (fang 方) with a side length of 1,000 paces (bu 步, see weights and measures), which corresponded to an area of 41 qing 頃, 66 mu 畝 and 160 bu (or 4,166.67 mu). The four corners of this square were marked by earth piles or trees. Each year in the ninth lunar month (see calendar) an official was dispatched supervising the surveying of the land and the assessment of the soil quality in one of five categories. This was recorded in a ledger and drawn in a draft map with black and red ink, and the tax quota of the district accordingly assessed.
The survey was executed by a tighing chief (da jiatou 大甲頭, see lijia system 里甲) with three assistants (xiao jiatou 小甲頭). There were four different types of ledgers, namely field ledgers (fangzhang 方帳 or 方賬), estates ledgers (zhuangzhang 莊帳 or 莊賬), tithing records (jiatie 甲帖), and household records (hutie 戶帖, see household registers). Six months after the assessment, the records were declared legally binding, if no one protested. Apart from taxation purposes, the registers could be used in any case land was divided or sold. The project was only implemented around the capital Kaifeng 開封 (today in Henan), but landowners heftily argued against the new law because it deprived them of much of their freedom of arranging land lots for individual purposes – or simply, to avoid taxes. In 1085 therefore, the law was abolished. At that time an amount of 2.48 million qing of land had been surveyed, making out 54 per cent of the arable land of Song China. Emperor Huizong 宋徽宗 (r. 1100-1125) made a further attempt, but the practical implementation was too complex, for which reason the reform was given up after 1120.