Customs duty obligation persists despite confiscation; contractual guarantor remains liable to pay unpaid customs duty under the Act. Import duty is an independent, exigible obligation arising on importation and remains payable notwithstanding confiscation or imposition of penal consequences; a contractual third party liable under an agreement must pay the customs duty as if it had imported the goods, and recovery may be effected where auction proceeds fall short of the leviable duty.