Customs Act Article 42

To verify the correct customs value of imported goods, Customs may take the following investigation measures, and the person investigated shall not evade, hinder or refuse such investigation:1. Examining any other documents concerning the price of the imported goods sold by the seller to the buyer;2. Making inquiries into the transaction value or deductive value of the imported goods or identical or similar goods, and examining past records of customs values assessed for previous shipments;3. Investigating account books and vouchers related to the imported goods or identical or similar goods of other sellers;4.Exploring any other evidence pertinent to valuation.
中文原文 關稅法第42條
海關為查明進口貨物之正確完稅價格,得採取下列措施,被調查人不得規避、妨礙或拒絕:
一、檢查該貨物之買、賣雙方有關售價之其他文件。
二、調查該貨物及同樣或類似貨物之交易價格或國內銷售價格,及查閱其以往進口時之完稅價格紀錄。
三、調查其他廠商出售該貨物及同樣或類似貨物之有關帳簿及單證。
四、調查其他與核定完稅價格有關資料。

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