Commercial samples import rules allow duty exemption subject to value, quantity limits and re export obligations. Importation of bona fide commercial samples is permitted duty free subject to per unit and annual value/quantity limits, exclusions for prohibited goods, and procedural undertakings. Prototypes of engineering machinery have specific treatment: lower value prototypes may be admitted duty free if rendered unsaleable after demonstration; higher value machines require duty deposit or bank guarantee and an undertaking to re export within a prescribed period. Customs may investigate breaches, seal high value machinery in transit, and limited extensions for re export may be allowed by the Customs authority.