Customs clearance by post: postal imports and exports require declarations, examination, duty assessment, and postal collection procedures. Customs examination and assessment of postal imports and exports are effected at notified Foreign Post Offices and Sub Foreign Post Offices: postal authorities deliver parcel bills and sender declarations to Customs; appraisers identify parcels for detention where particulars are deficient or suspected to be misdeclared, compute duty using declared values converted at the ruling exchange rate on the presentation date, note rates and amounts on parcel bills, and the Post Office recovers assessed duties from addressees at delivery while detained or prohibited consignments remain under Customs custody.