According to Korea Post, an example postal code for Seoul, South Korea is 132-798. Postal codes should be placed underneath the addresses of both the sender and receiver.
According to Anglo Info, the first three digits are determined by the province, town or zone of an address, while the final three are determined by the delivery zone, box or building. Seoul postal codes always start with 1. Korea Post advises people sending mail to South Korea to always include Seoul on the city line to ensure that mail does not go to the Democratic People's Republic of Korea (North Korea).