Regulations Governing Enrollment in Postal Simple Life Insurance Policies Article 14

If the proposer applies to change the beneficiary, or if the proposer died and his/her heir assumes the insurance contract, a notice of contract change shall be prepared, signed or sealed by the insured and submitted to the handling office of Chunghwa Post along with the policy.
中文原文 郵政簡易人壽保險投保規則第14條
要保人申請變更受益人或要保人死亡,由其繼承人承受保險契約者,應填具契約變動通知書,經被保險人簽名或蓋章後,連同保險單一併送交經辦郵局辦理。

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