Detention and seizure of goods require payment or security for release, with notice, hearing and a limited statutory period. Section 129 authorises detention and seizure of goods, conveyances and related documents in transit for contraventions, and provides three release routes: (a) payment of tax and penalty equal to one hundred per cent. of the tax (with a capped alternative for exempted goods) when the owner comes forward; (b) payment of tax and penalty equal to fifty per cent. of the goods' value reduced by tax paid (with a capped alternative for exempted goods) when the owner does not come forward; or (c) furnishing prescribed security equivalent to the amount under (a) or (b). The proper officer must serve orders, issue notice specifying tax and penalty, allow a hearing, and if unpaid after seven days initiate further proceedings, with a reduced period for perishable or hazardous goods.