Name Act Article 11

A person who was not using his/her legal name as stipulated in Articles 6 and 7 before the Act took effect shall apply to change the name used at his/her original public or private sector enterprise, entity (organization), association, or school to his/her legal name. Suppose the person did not use his/her legal name as stipulated in Article 6. In that case, he/she may apply for a change of legal name at his/her household registration office according to his/her name on a diploma, employment certificate, license, or other form of identification.A name change under the preceding paragraph may be granted only once.
中文原文 姓名條例第11條
在本條例施行前,有第六條、第七條所定未使用本名情事者,應於本條例施行後,向原權責公民營事業機構、機關(構)、學校、團體申請更正為本名;有第六條所定未使用本名情事者,得以學歷、資歷、執照、其他證件或其他足資證明文件之名字為準,向戶政事務所申請更正本名。
前項之申請,以一次為限。

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