Customs duty must be assessed at declaration date regardless of barter contract value or tax audit findings.

The Supreme Court dismissed the company's appeal against a customs decision regarding fuel oil imported under a barter agreement. The court found that the lower administrative court erred by relying on tax audit protocols to adjust the customs value, violating the strict rule that duties are fixed at the time of declaration. Consequently, the Supreme Court restored the original customs decisions, affirming that barter settlements and tax valuations cannot retroactively alter the declared customs value.