Customs Act Article 32

I. If the customs value of the imported goods cannot be determined under the provisions of Articles 29 and 31, the customs value shall be based on the transaction value of similar goods sold for export to the Republic of China, exported at or about the same time as the goods being valued. In applying this Article, a reasonable adjustment shall be made to take into account differences in value attributable to commercial levels, quantity, transport costs, etc.II.The term "similar goods" referred to in the preceding paragraph means goods which, although not the same in all respects, are produced in the same country, perform the same functions, have like characteristics and like component materials, as the goods being valued, and are commercially interchangeable with the goods being valued.
中文原文 關稅法第32條
進口貨物之完稅價格,未能依第二十九條及前條規定核定者,海關得按該貨物出口時或出口前、後銷售至中華民國之類似貨物之交易價格核定之。
核定時,應就交易型態、數量及運費等影響價格之因素作合理調整。
前項所稱類似貨物,指與該進口貨物雖非完全相同,但其生產國別及功能相同,特性及組成之原材料相似,且在交易上可互為替代者。

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