Reflecting the reigns of different British sovereigns and, most clearly, the return of Hong Kong to China, Hong Kong’s stamps have undergone a great many changes, but postage due labels have remained unaffected. Before these labels were introduced, regular stamps were used to collect unpaid or underpaid postage. After their launch, however, post offices would add them to mail to remind postmen to collect the postage due from the addressees.

The first set of Hong Kong’s postage due labels was issued in 1923, and they featured a scale with an overweight letter on the left and a hanging tray on the right to suggest that the postage paid was insufficient. In 1987, new postage due labels were introduced that used the Chinese word for ‘due’, while another design has been used since 2004. The highest denomination of the postage due labels is $10 in 2012. When a large amount of postage is due, post offices will frank internationally recognised impressions in green ink using postage due meters.