Enforcement Rules of the Name Act Article 10

Once any person who applies for any matter in Article 4 or Article 5 has registered and has the documents, said person may file with the originally-issued agency or competent authority concerned for registration of his/her full name alteration and alteration of registration.
中文原文 姓名條例施行細則第10條
依第四條及第五條規定申請之各類案件,於登記後,其有證件者,得向原發證機關或其主管機關為變更姓名之登記及改註證件。

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