On-site post-clearance audit requires advance notice and permits inspections, sampling, and an opportunity to clarify findings before report. On-site post-clearance audits require the Superintendent of Customs and Central Excise or Appraiser to give at least fifteen days' notice, to gather prior information, visit and audit at the importer's or exporter's premises, inspect goods, take samples and copy documents, and to inform parties of objections before preparing a draft report so they may offer clarifications; voluntary payments when parties agree with findings are to be recorded in the audit report.