I had my SIM from before the days they needed ID. When the rules were changed, I had to produce two forms of ID else the card would be blocked. They accepted my UK passport, but wouldn't accept anything else I had. They said it had to be Taiwanese. (I had a UK driving licence, credit cards etc.)

There was not alternative but to register it in a friend's name. I was annoyed about that having used the card for years. Also to me it seemed to somewhat defeat the purpose of the scheme - ie to knowingly register the SIM to the wrong person. (OK no comments pls, I know the answer to that one.)

Then when I worked in Taiwan, I re-registered it back to myself using my alien resident's card and passport.

Perhaps they are not so strict these days. I believe at the time other SIM providers were more flexible.