Enforcement Rules of the Household Registration Act Article 5

After receiving notice from immigration authority for a concerned party depart from the country for more than two years, household registration office shall notice the concerned party to apply for Move-out Registration in a certain period of time. In case the concerned party doesn’t apply for Move-out Registration in the certain time limit, household registration office may proceed with the Moving-out Registration at its discretion pursuant to the Article 42 of this Act, and then notify the concerned party.
中文原文 戶籍法施行細則第5條
戶政事務所應於接獲入出國管理機關之當事人出境滿二年未入境人口通報時,通知應為申請之人限期辦理遷出登記;未依限辦理遷出登記者,戶政事務所於查核當事人戶籍資料後,得依本法第四十二條規定逕行為之,並通知應為申請之人。

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