Transaction value principle governs bulk liquid import duty assessment; invoice price, not measured quantity, determines ad-valorem liability. For bulk liquid imports, where customs duty is ad-valorem the assessment must be based on the invoice price as the transaction value regardless of shore tank or ship ullage measurements; for deliveries to multiple ports the value must be apportioned by intended discharge quantities. Where duty is specific, quantity determined by shore tank measurement remains relevant and earlier Circular No.96/2002 applies to specific-rate cases; pending provisional assessments should be finalized accordingly.