Self-assessment of import and export duty subject to risk-based verification, reassessment, and provisional clearance on security. Importers and exporters must self-assess classification, value, duty rate and exemption claims when filing entries; such declarations are subject to selective risk-based verification including examination, testing and document production, and may be reassessed by the proper officer with a speaking order on request. Where verification or final assessment cannot be completed promptly or the declarant cannot determine duty, provisional assessment is available upon furnishing security for any eventual duty deficiency; declarants must also declare the Standard Unit Quantity Code for proper assessment and statistics.