Yellow household registers (huangji 黃籍) was a designation for regular household registers used during the Jin 晉 (265-420) and Southern Dynasties 南朝 (420-589) periods. An imperial order of the Jin dynasty required that the registers consist of wooden slips (zha 札, today usually termed mudu 木牘) with a length of 1.2 chi 尺 (see weights and measures). These slips were preserved against insects by treatment with a yellow substance (huangbo 黃檗, Phellodendron amurense?), hence the name. In later years, the wooden slips were replaced by paper, which was treated in the same way.
During the Eastern Jin period, apart from the regular, yellow registers, white registers (baiji 白籍) came into use. They were particularly used for recording the households of refugees from the north who had settled in temporary "refugee (or exile) provinces" (qiaozhou 僑州郡), "refugee commanderies" (qiaojun 僑郡) or "refugee districts" (qiaoxian 僑縣), and would eventually return to their homelands. Their status as temporary residents allowed to use registers without preservative agents, so their documents remained white or whitish.
In contrast to native inhabitants of southeast China, these temporary settlers were not obliged to deliver taxes in kind and labour service (yaoyi 徭役) to the government. Only when it became clear that northern China could not be reconquered at once, and under fiscal distress, the Eastern Jin 東晉 (317-420) government decided to give the "refugee residents" land (by splitting off land from other administrative units), to transform the white into yellow registers, and to claim the respective duties from the new residents.
In the following centuries, the numbers of incoming refugees from northern China did not totally decline, so the custom of provisional white registers, continued. Wrong statements about the number and size of households liable for tax payment and corvée labour led to regular inspections of households (jian ji 檢籍) during the Liu-Song 劉宋 (420-479) and the Southern Qi 南齊 (479-502) periods. In some cases, landowners had their land recorded in a refugee zone, which freed them from tax obligations. In case of uncovering such a case, the respective "fake household" was eliminated (que ji 卻籍).
The term "yellow register" was also used during the Wei 曹魏 (220-265) and Jin periods for documents recording the rank status of officials and their families. Copies went to the Ministry of Education (situ fu 司徒府). The word huangji remained during the Tang period 唐 (618-907) a term for regular registers of "office land" (zhitian 職田) whose revenue was to cover the salary or "expenditure land" (gongxietian 公廨田) used to meet the cost of administration.