Interest on duty credit: charging when input-duty credit is varied, and retrospective rebate rule for export inputs. Amendment adds rulemaking authority to specify interest on amounts referenced to 'outside India' and inserts a provision to enable charging and payment of interest where credit for duty paid or deemed paid on goods used in manufacture of excisable goods is subsequently varied. It also replaces 'form' with 'form and manner' for procedural specification and permits rules to give retrospective effect to rebates on duties for inputs used in export goods from no earlier than the date of changes in input duty rates.