Hong Kong does not have any zip or postal codes. According to postal workers in the city, the city is so small that it is easy to deliver the mail without sorting it based on postal codes.
If someone from Hong Kong orders something from an online vendor and requires a postal code, they can simply use five zeros or place HK in that field.
Hong Kong is a special administrative region of China, and as such, it doesn't have all of the same rules or programs as some of the other areas of the country. All of the other areas of China, from the big cities to the rural areas, have postal codes. The only exception is Macau, the country's other special administrative region.
Although postal codes are used to help sort mail in countries all over the world, the phrase ZIP code is only used in the United States. ZIP stands for zone improvement plan, and it refers to a plan that was put into place in 1963. By assigning a specific five-digit number to each area, the United States Post Office assumed that its workers could sort the mail more accurately and expediently.