Enforcement Rules of the Labor Insurance Act Article 23

In the event that the insured persons are transferred in the insured units with the same affiliation, the transferring units shall fill out the transfer-out part of the application forms for transfer of insurance coverage and forward them directly to the receiving units. The receiving units shall fill out the receiving part of the forms and submit both parts to the insurer. The effectiveness of the transfer of insurance coverage shall be set on the date when the application forms for transfer of insurance coverage reach the insurer. In case of mailing, they shall be set in accordance with the post-marks of the original sending post offices.
中文原文 勞工保險條例施行細則第23條
被保險人在有同一隸屬關係之投保單位調動時,應由轉出單位填具轉保申報表轉出聯,逕送轉入單位,由轉入單位填具該表轉入聯一併送交保險人,其轉保效力自轉保申報表送交保險人之當日起算,郵寄者以原寄郵局郵戳為準。

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