Duty assessment for warehoused imports requires bond-based security at warehousing; duty payable on ex-bond clearance under applicable rate. A distinct Bill of Entry is used for warehousing with the same documentary and assessment requirements as home consumption; duty is assessed at warehousing to secure liability and is secured by execution of a Bond. Duty is payable only at ex-bond clearance when an Ex-Bond Bill of Entry is filed, and the applicable rate is the rate in-force on the date of filing the Ex-Bond Bill.