Transaction value principle governs customs valuation, with hierarchical alternative methods applied when declared value is doubtful. The primary basis for customs valuation is the transaction value, defined as the price actually paid or payable including payments to third parties as a condition of sale; if valuation conditions are unmet or doubts exist about declared value, valuation proceeds by a hierarchical sequence of methods: comparison with identical goods, comparison with similar goods, deductive resale-based method, computed cost-based method, and a fallback method applying earlier approaches with flexibility.