Taiwanese county code
The five-digit code identifying a Taiwanese county, city or special municipality, kept by the Ministry of the Interior.
The code comes from the household registration system of the Ministry of the Interior, whose tables replaced an older classification from the statistics directorate in 2017.
Five digits, and the shape depends on the tier. A county or provincial city sits under a province: 100 for Taiwan Province followed by two digits, so Changhua County is 10007 and Chiayi City 10020. Kinmen and Lienchiang sit under Fujian Province and begin 09 instead, which is why a rule expecting every code to start with 100 rejects them. A special municipality has no province above it and takes a two-digit number followed by 000, so Kaohsiung is 64000 and Taipei 63000.
The register keeps abolished units. Taipei County 10001, Kaohsiung County 10012 and Tainan County 10011 ceased to exist when those areas were upgraded to municipalities in 2010, but their codes remain listed.