The Employment Gold Card Super-Thread

I think he maybe has that option because he was already in NHI by his previous employment. He can change his status.

you can check here. Contribution of employees is 30%, but if you are self-employed, it is 100%.

How Premiums Are Calculated
https://www.nhi.gov.tw/english/Content_List.aspx?n=B9C9C690524F2543&topn=46FA76EB55BC2CB8


Edit:
I found “Self-employed Independent professionals and technical specialists” in Category 1 are people with official certificates. Self employed individuals may be “other individual” in Category 6, unless they are certified specialists (Category 1) or belong to some unions(Category 2).