http://glrs.moi.gov.tw/EngLawContent.aspx?Type=C&id=297
Article 16 In accordance with paragraph 1, Article 28 of the Act, aliens over 14 years of age inside Taiwan’s national border, shall carry on his/her person the passport, the Alien Resident Certificate, or the Alien Permanent Resident Certificate.
https://www.moi.gov.tw/english/english_law/law_detail.aspx?sn=332
Article 28 An alien, at the age of fourteen (14) or up, who has entered the State for a visit, residence or permanent residence, shall always carry his/her passport, Alien Resident Certificate, or Alien Permanent Resident Certificate.
National Immigration Agency or public servants under other laws and orders can demand aliens to produce the documents stated in the preceding Paragraph while performing official duties. With respect to requirements and a procedure for requests for production of certificates and production of certificates, the provisions of Chapter 2 of the Police Duties Enforcement Act shall apply mutatis mutandis.
I don’t immediately see that last act, but I would assume one could be detained until their identity can be determined and it decided that they are not in the country illegally. I doubt there are other penalties, but not sure
This is it:
https://law.moj.gov.tw/Eng/LawClass/LawAll.aspx?PCode=D0080145
When it is definitely impossible to verify a person’s identity by using the measures set forth in subparagraphs 2 and 3 of the preceding paragraph, the police may take the person to the police agency for further verification. The police shall not use coercive power unless they are resisted and the duration of the verification shall not exceed three hours starting from the time the person is stopped. The police shall also immediately report the identity verification to the Duty Command Center and inform the relative, friend, or lawyer as requested by the person.