Notifications (zhaohui 照會) were documents sent by an institution to another one of slightly lower rank. This type of official documents was introduced during the Song period 宋 (960-1279) and remained in use until the end of the imperial time.
In the early form, documents of this type were closed by the words "please be informed that" (qing zhaohui 請照會) or "be apprised of this” (yang zhaohui 仰照會). Zhaohui notifications did not require an answer by the recipient. During the Ming period 明 (1368-1644), zhaohui notifications were used on relatively high levels of the bureaucracy. The Qing 清 (1644-1911) administration used them mainly for communication between the military and the civilian parts of the local administration, e.g. a governor-general (zongdu 總督) addressing a regional commander (zongbing 總兵), a provincial commander (tidu 提督) notifying one of the provincial commissioners or circuit intendants (sidao 司道), a regional commander informing a first-class prefect or district magistrate, or a regional vice commander (fujiang 副將) writing a letter to a second-class prefect or a district magistrate. Inside the civilian sphere, zhaohui notifications were only used when first-class prefects instructed heads of directly administered prefectures (zhilizhou zhizhou 直隸州知州). In this case, the date was written in black ink (so-called heibi zhaohui 墨筆照會) to express some kind of appreciation, while all others used red ink for indicating the date of issuing, a colour normally reserved for the emperor.
Before the First Opium War (1839-1842), the governor-generals of Liang-Guang 兩廣 used zhaohui notifications when dispatching letters to British officers. The Treaty of Nanjing from 1842 stipulated the continued use of this type of document, but this meant that zhaohui-type documents were regarded as "communication" among persons of equal standing (pingxing wen 平行文), and not anymore such to institutions of slightly lower rank. In this diplomatic function, zhaohui communication notes are still used today.