Letter of undertaking allowed for concessional duty where no show-cause or rule-based enforcement proceedings exist. The amendment inserts a proviso to rule 3 permitting a manufacturer to provide a letter of undertaking for removal of goods at concessional duty where no show-cause notice has been issued under the Act and where no action is proposed under notifications issued pursuant to rules governing credit reversal and related proceedings, thereby making absence of such proceedings a sufficient condition for acceptance of the undertaking.