Provisional assessment permits provisional duty payment with bond, interest on late payments and limited refund exceptions. Provisional assessment permits payment of duty on a provisional basis upon written request and specification by the Assistant or Deputy Commissioner; it requires a prescribed bond with surety or security to secure payment of any difference on final assessment. Final assessment must be completed as soon as information is available and within six months, subject to authorised extensions. Interest is payable on unpaid provisional amounts from the day after the due date until actual payment. Refunds arising from final assessment bear interest but are to be credited to the Fund unless attributable to duty not passed on by the manufacturer or buyer, in which case refund may be paid to the applicant.