Regulations Governing the Determination of Country of Origin of Imported Goods Article 4-2

The Customs Authorities at the place of importation shall finalize the determination of the origin of the imported goods within two months after the import declaration date.The determination period set forth in the preceding paragraph may be extended for two months in the event that further investigation is required. However, the extension is limited to one time only, and, in this case, the obliged tax payer shall be informed of the reason for such extension.
中文原文 進口貨物原產地認定標準第4-2條
進口地關稅局應自貨物申報進口之日起二個月內,完成原產地之認定。
前項認定期間,得因查核需要予以展延二個月,但以一次為限,並應將展延事由通知納稅義務人。

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