Provisional assessment: bond and prescribed security secure payment of any duty deficiency under customs provisional estimates. Provisional assessment requires the proper officer to estimate provisional duty while the importer or exporter must execute a bond undertaking to pay any duty deficiency and furnish prescribed security for the duty deficiency. Security may be provided as a bank guarantee or a cash deposit, at the importer's option. Central Board circulars provide consolidated procedural guidance for provisional assessment and have been updated to reflect administration of rules of origin under trade agreements.