The pingmifa 平米法 "field tax adjustment method", also called "adjustment meethod of the tax and additional levies" (junzheng jiahao fa 均征加耗法), was a measure to readjust tax payment carried out from the mid-Ming period 明 (1368-1644) on, and restricted to the lower Yangtze region.
The field tax was extraordinarily high in the prefectures of Suzhou 蘇州 and Songjiang 松江 and reached a level of up to 7 dou 斗 or even 1 shi 石 per mu 畝 of land (see weights and measures), in addition to labour corvée. Yet while some peasants were fleeced in this way, others paid less exploitative taxes. The amount of grain delivered per land differed from person to person, and even the conversion rate for taxes delivered in money (zhese 折色) insteat of in rice (bense 本色). While some peasants payed 2.5 qian 錢 (a weight unit) per shi of harvested rice, other paid as much as 7 or 8 qian.
In 1433 therefore, the grand coordinator (xunfu 巡撫) of Jiangnan 江南, Zhou Chen 周忱, reformed the local tax assessment system (keze 科則). Persons having formerly paid high taxes, were allowed to pay taxes in money and were levied less than before. Those who had paid 7 dou per mu, for instance, were taxes at an amount of 2.5 qian of money per shi of grain, with a ceiling amount of 1.75 qian per mu of land. Those who had earlier escaped high taxation, had from then on to deliver taxes in kind (grain), at a higher rate per mu of land. In addition to this outbalancing earlier unfairness, official land (guantian 官田) and private land (mintian 民田) was taxed at the same rate.
The transport-loss surcharge (hao 耗) was also balanced out and applied equally to everyone and each type of field, regardless of the size of the household. It was directly levied as a fix proportion of the basic tax, which in turn depended on the quality of the soil, the field size, and the size of the household. Because Emperor Chengzu 明成祖 (r. 1402-1424) transferred the main seat of the government to the Northern Capital Beijing, transport cost, and also the loss of grain under way, became higher, so that the transport-loss surcharge was as high as a third or even half of the main tax, in other places just a fourth or a fifth. Any amounts of grain surpassing the tax quota would be stored in the local granaries as reserves for the future.
From the Tianshun reign 天順 (1457-1464) on the system was extended to the prefectures of Hangzhou 杭州, Jiaxing 嘉興 and Huzhou 湖州. In 1537 the sytem was somewhat altered on the initiative of grand coordinator Ouyang Feng 歐陽鋒 and prefect Wang Yi 王儀, so that the original aim of the reformed tax system was better realized. In this change the system was called zhengyifa 征一法.