During the first half of the Tang period 唐 (618-907) the tax system consisted of three components, namely the field tax (zu 租), household tax (diao 調), and labour corvée (yong 庸, see yaoyi 徭役). This pattern had been created by the Northern Wei 北魏 (386-534) as a complement of the equal-field system (juntian zhi 均田制), by which the government lent out arable land to the peasantry, which in turn delivered taxes and services. The average size of land allotted under the Tang was 80 mu 畝 (see weights and measures) of arable land (koufentian 口分田) per male person (dingnan 男丁, nanding 男丁) and 20 mu of inheritable land for planting mulberry trees etc. (yongye tian 永業田). Household registers helped to identify tax-liable persons (kekou 課口) and tax-liable households (kehu 課戶).
Emperor Gaozu 唐高祖 (r. 618-626) adopted this system in 624 and specified the amounts of taxes to be paid. Each male person paid 2 shi 石 "bushels" of millet (su 粟) or 3 shi of rice (dao 稻) as field tax (in reality, the amount ranged between 0.6 and 1.2 shi, depending on the average harvest "income"), 2 "cords" (zhang 丈) of silk fabric of various qualities (shi 絁, juan 絹, ling 綾) and 3 "ounces" (liang 兩) of silk floss (mian 綿) in "mulberry villages" (canxiang 蠶鄉), or alternatively 2 cords and 4-5 "ells" (chi 尺) of fabric and 3 "pounds" (jin 斤) of hemp for linen as a household tax in "hemp villages" (maxiang 麻鄉).
Additionally, each adult male served 20 days per year (or 22 in years with an intercalary month) in official projects (called zhengyi 正役 "normal labour service" or keyi 課役 "tax service"), or alternatively paid 3 more ells of tough silk (juan 絹) or 3.6 ells of other fabric for each day he was unable or unwilling to serve. In case the government requested services for a longer period of time, this was offset with the other taxes: 15 days of additional labour service substituted the household tax, and 30 days both household and field tax. Theoretically it was not allowed to distract peasants from their work for more than 50 days a year. Natural disasters and pests (like locusts) were taken into consideration of this model, and the government resigned the payment of the field tax, or in worst case, waived all taxes. Yet apart from the zuyongdiao tax levied on each male adult there were still the household tax (hushui 戶稅) paid in money and the land tax (dishui 地稅) paid in grain.
The household tax was levied in the eighth month of each year and the products were sent to the capital during the ninth month. The time of harvest naturally changed from region to region, and the tribute grain was sent to the capital granaries in the eleventh month of each year. The products were handed over to the Court of the National Granaries (sinongsi 司農寺), the Court of the Imperial Treasury (taifusi 太府寺), the Directorate for the Palace Buildings (jiangzuojian 將作監) or the Court for the Palace Revenues (shaofusi 少府寺). Alternatively, grain and fabric was sent to nearby garrisons to feed the troops.
There was a considerable number of persons exempted from labour corvée, mainly the members of the imperial house and of ennobled persons, but also state officials of rank 5 and higher, as well as persons granted the honorary titles of "filial son" (xiaozi 孝子), "obedient grandson" (shunsun 順孫), "righteous man" (yifu 義夫) or "chaste woman" (jienü 節婦). In addition to that, all state officials, elderly persons, the sick, women and concubines, private militiamen (buqu 部曲), maids (kenü 客女) and serfs and slaves (nubi 奴婢) were not liable for paying the household tax.
The revenue from the tripartite tax system was considerable. Figures in Du You's 杜佑 (735-812) statecraft encyclopaedia Tongdian 通典 speak of 8.2 million taxpayers delivering grain with an amount of 12.6 million shi, 7.4 million bolts (1 pi 匹 "bolt"= 4 cords), 18.5 million tun 屯 (1 tun = 6 ounces) of silk floss, and 16.05 million duan 端 (1 duan = 5 cords) of other fabric. The household and field tax levied from 8.9 million households run to 22.2 million strings (guan 貫) of cash and 12.46 million shi of grain. These figures make for three fourths of the total revenue of the Tang government during the Tianbao reign-period 天寶 (742-756).
In the early years of the Tang the tripartite tax system put a comparatively modest burden on the shoulders of the peasantry and nonetheless supported the reconstruction of the economy throughout the empire and ensured that the state coffers obtained a stable and sizeable tax revenue. After the rebellion of An Lushan 安祿山 (703-757) these amounts shrank considerably because the central government lost the grip on the provinces. The tax system was therefore in the late eighth century replaced by the twice-taxation system (liangshuifa 兩稅法).
Apart from the political situation, one reason for the abolishment of the tripartite tax system was that it did not fully correspond to the equal-field system, but was more often based on the household registers which were much easier to consult than the complex field allotment system, particularly during the eighth century, when the population grew.
A third reason was the increasing appropriation of land by the elite. Peasants under financial distress sold their land to the local gentry and became tenant farmers which were not liable for tax payment.