Zhengyifa 征一法 "unified taxation method", also called juntanfa 均攤法, qiantanfa 牽攤法, qianhaofa 牽耗法 or juntianfa 均田法 (not to be confounded with the juntianfa method of this name used during the early Tang period 唐, 618-907) was an adjustment of the the field tax carried out during the Ming period 明 (1368-1644), first tentatively in ten prefectures round around the Southern Capital Nanjing, and then also in other prefectures of the southeast.
Before the adjustment the common method of levying the field tax was the so-called field tax adjustment method (pingmifa 平米法). In 1536 the Minister of Rites (libu shangshu 禮部尚書), Gu Dingchen 顧鼎臣, suggested to carry out a new survey of all taxable field, in order to discover unregistered land (yinnitian 隱匿田). A year later the prefect (zhifu 知府) of Jiaxing 嘉興, Zhao Ying 趙瀛, suggested to abolish the distinction between official land (guantian 官田) and private land (mintian 民田), and to redefine the tax classes, beginning with a lowest amount of 3 sheng 升 per mu 畝 of land (see weights and measures).
The grand coordinator (xunfu 巡撫) of the province, Ouyang Duo 歐陽鐸, and the prefect of Suzhou 蘇州, Wang Yi 王儀, began to implement this system in Suzhou. They merged the payment for the local village service (lijia yin 里甲銀, see lijia 里甲) and the common service (junyao yin 均徭銀, see yaoyi 徭役) with the poll and field tax. In 1538 all arable field in the prefecture was classified according to its fertility and the annual tax quota calculated according the fertility and the size of the field owned. The average tax for one mu of land was 3 dou 斗 per year, yet this amout was also payable in money, with a conversion rate of 5 qian 錢 per dan 石 of rice.
The name of the new taxation method is derived from its designationin the taxation registers, zheng yi ding e 征一定額 "fix quota levied at one go". The system was thereupon spread to other districts, but not applied in the same way. In Songjiang 松江, Changzhou 常州 and Zhenjiang 鎮江, for instance, the difference between official and private land remained valid, and both types of land were taxed differently.
In 1853 the likin tax (lijin 釐金) was introduced, which was a more modern type of commercial tax.