Regulations Governing Book-Entry Operations for Centrally Deposited Securities Article 14

The participant's account books, the customer's account books, and the entry vouchers shall be maintained for a period of at least 15 years from the entry date.
中文原文 有價證券集中保管帳簿劃撥作業辦法第14條
參加人帳簿、客戶帳簿及其入帳憑證應自登載之日起至少保存十五年。

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