Household Registration Act Article 18

Any address alteration made within the same domiciliary area of jurisdiction (township, city, district) for over 3 months shall be subject to Address Alteration Registration.
中文原文 戶籍法第18條
同一鄉(鎮、市、區)內變更住址三個月以上,應為住址變更登記。

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