Customs Act Article 98

The duty-payer or exporter and any related person shall maintain all records, documents, accounting books and relevant computer files or data bases relating to the imported or exported goods for five years beginning on the next day of the day on which the imported or exported goods were released.
中文原文 關稅法第98條
關稅納稅義務人或貨物輸出人及其關係人對於與進出口貨物有關之紀錄、文件、會計帳簿及相關電腦檔案或資料庫等資料,應自進出口貨物放行之翌日起,保存五年。

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