SECTION 18.

(1) Notwithstanding anything contained in this Act but without prejudice to the provisions of section 46, -

(a) where the importer or exporter is unable to make self-assessment under sub-section (1)of section 17 and makes a request in writing to the proper officer for assessment; or

(b) where the proper officer deems it necessary to subject any imported goods or export goods to any chemical or other test; or

(c) where the importer or exporter has produced all the necessary documents and furnished full information but the proper officer deems it necessary to make further enquiry; or

(d) where necessary documents have not been produced or information has not been furnished and the proper officer deems it necessary to make further enquiry, the proper officer may direct that the duty leviable on such goods be assessed provisionally if the importer or the exporter, as the case may be, furnishes such security as the proper officer deems fit for the payment of the deficiency, if any, between the duty as may be finally assessed and the duty provisionally assessed.

(Above sub-section (1) SUBSTITUTED vide THE FINANCE BILL, 2011)

[OLD - (1) Notwithstanding anything contained in this Act but without prejudice to the provisions contained in section 46 -
(a) Where the proper officer is satisfied that an importer or exporter is to produce any document or furnish any information necessary for the assessment of duty on the imported goods or the export goods, as case may be; or

(b) where the proper officer deems it necessary to subject any imported goods or export goods to any chemical or other test for the purpose assessment of duty thereon; or

(c) where the importer or the exporter has produced all the necessary documents and furnished full information for the assessment of d but the proper officer deems it necessary to make further enquiry for assessing the duty,
the proper officer may direct that the duty leviable on such goods may, pending the production of such documents or furnishing of such information or completion of such test or enquiry, be assessed provisionally if the importer or the exporter, as the case may be, furnishes such security as the proper officer deems fit for the payment of the deficiency, if any, between the duty finally assessed and the duty provisionally assessed.]

(2) When the duty leviable on such goods is assessed finally by the proper officer [OLD- in accordance with the provisions of this Act, ] then 

(Above changes vide THE FINANCE BILL, 2011)

(a) in the case of goods cleared for home Consumption or exportation, the amount paid shall be adjusted against the duty finally assessed and if the amount So paid falls short of, or is in excess of the duty finally assessed, the importer or the exporter of the goods shall pay the deficiency or be entitled to a refund, as the case may be;

(b) in the case of warehoused goods, the proper officer may, where the duty finally assessed is in excess of the duty provisionally assessed, require the importer to execute a bond, binding himself in a sum equal to twice the amount of the excess duty.