Regulations Governing Interview Implementation by the National Immigration Agency, Ministry of the Interior Article 4

With nationals without household registration in the Taiwan Area, people of the Mainland Area, and residents of Hong Kong or Macau, the NIA may first issue such a person an entry permit before they enter the Taiwan Area, and then conduct an interview with them at an NIA-designated place in the airport/seaport once they enter the Taiwan Area.
中文原文 內政部入出國及移民署實施面談辦法第4條
移民署得對臺灣地區無戶籍國民、大陸地區人民、香港或澳門居民先予核發入國(境)許可;俟其入境時,至移民署設於機場、港口之指定處所接受面談。

English translation for reference only; the Chinese text prevails. Not legal advice.